Powerlifting is a more modern sport than weightlifting but is still considered a valid and time-honored system for testing strength. Shying away from the classical attempts to move weight completely overhead from the floor, powerlifting is a competition of limit strength as opposed to explosiveness, and taxes the entire body in three different ways.
Limit strength is a function of the maximal force you can apply, as opposed to the explosive strength required in weightlifting. Some people consider the name "powerlifting" to be a misnomer because in physics terms power is a function of force and time, with a shorter more explosive lift in theory being higher in terms of power output.
The sport is similar to weightlifting in that it was weight classes and three attempts to complete a lift per event. Because it has three events, there are nine lifts in total you must complete, and three events you must complete in order to be considered in the final scoring. The genius of the sport however is that an advantage in one event is actually a disadvantage in another.
The classic weightlifter build is compact, with relatively short limbs in a specific proportion. And short limbs come in handy - someone with shorter arms will not have to press a bench press out so far, making it comparatively easier. That being said, the guy who's great at the bench press will suffer in the deadlift because of having to pull the bar farther off the ground. In short, because the three lifts have different strengths and weaknesses, it's possible for a larger number of people to have potential in the sport.
The three lifts are the squat, the deadlift, and the bench press. There are other variants of competition, like bench press only meets or push pull (bench/deadlift). But the standard is "the big three".
The squat involves the lifter putting the bar on his or her shoulders, typically lower on the back than in weightlifting training. The lifter then sits backwards as opposed to straight down, getting a good stretch in the hamstrings as the lifter breaks parallel with the thigh, meaning that the hip is lower than the knee. The lifter then stands back up. It is an incredibly taxing lift that involves the entire body. The original IPF version of the lift required the lifter to unrack the bar off a stand, take one step backwards, complete the lift and then step forwards. But because that wasn't explicitly written into the rules at first, an American lifter by the name of Fred Hatfield or "Dr. Squat" asked the staff to simply move the stands out of his way once he unracked the bar, and then replace them when he stood back up. Other lifters cried foul but upon review everyone realized that he hadn't actually broken any rules of the sport by doing so. Some federations now use a device called a "monolift" that instead of being a stand consists of two hooks that flip out of the way when unracked, and back into place to catch the bar after the lifter completes standing up, but the IPF now has the "step back, squat, step forward" rules.
The bench press involves a specialized apparatus consisting of a low squat stand combined with a flat padded bench. The lifter lies down on the bench with his head between the uprights of the stand portion. An assistant helps unrack the bar into position over the chest. The lifter then lowers the bar to his or her chest, pauses on the chest, and then drives the bar back up to full extension, at which point someone assists the lifter in replacing the barbell on the stands. The shoulders and buttocks must remain on the bench at all times. The feet must remain on the ground where they started. But the technique of bunching the shoulders under the lifter for stability has led to a technique in which the lifter creates a significant arch in the back, lowering the distance the bar must travel and allowing for more weight to be lifted.
The deadlift consists of a bar on the ground being taken in an over/under grip (one hand facing the lifter, the other hand away) with either a normal (knee-bend/squat position) or sumo (knees bent/feet very wide apart) stance. The lifter then stands with the bar until he is completely erect, and drops the bar to the platform once the lift is scored. The deadlift is hard because there is no "preloading" of the weight, the muscles don't absorb the gravity of a bar coming downwards, getting a bounce reflex off the bottom of the lift. It also results in some of the highest ever recorded blood pressures known to medical science with the very real risk of blackout.
The lifts as a whole put such stress on the body that bruising, burst blood vessels in the eyes, bleeding noses, haemorrhoids, or even a few instances of bleeding out of the eye sockets has occurred. That often-shared meme on the internet showing someone with a prolapsed anus is fake. Picture is real but did not come from a powerlifting or weightlifting meet, it was a spontaneous prolapse.
The highest poundage in each event is taken and a total of the best of all three events is combined to a final poundage score (kilometrage in IPF). The lifter with the highest total in the weight class wins, or in the case of a tie, the lifter with the lower bodyweight.
Supportive gear is almost always used. At the very least, extremely tight wrist wraps are used in the bench press and knee wraps prevent the knees from caving in during squats. Tight, thick leather belts are typically used in the squat and deadlift, both to support the spine from snapping but also to give the lifter something to push abdominal muscles into to keep a tight midsection. Competing in this level of equipment is referred to as "raw" or "raw with wraps". Some consider "raw" to be nothing but shoes and singlet, but many people consider wrist and knee wraps perfectly acceptable for this nomenclature. The wraps are no joke. Not only are they hardcore elasticated bandaging, the most modern versions, trade name "Sidewinder", actually tighten over time. And given that they are applied initially with extreme force binding the joint to near immobility and literal tourniquet effect to anything downstream, I've been literally too intimidated to try them.
Going into "equipped" lifting means that a squat suit, deadlift suit and/or bench shirt is used. These are exceedingly tight versions of a singlet and T-shirt, respectively, made from a thick, no-give polyester. Different federations allow different kind of equipment, but the strictest is the IPF, which only allows certain certified models of these with one ply of material to be used, and no "open back" shirts that allow the shirt to be put on like a reversed jacket. The evolution came from the practice of wearing tight jean T-shirts in order to stabilize the shoulder and give a bit of "bounce" off the chest, the trickiest and heaviest part of the lift. It's accepted in competition because the clothing also reduces the chance of injury by stabilizing the shoulders and spinal erectors. It's uncomfortable, cuts off circulation and needs specialized tailoring and is damn scary to put on - requiring lubricants, special equipment and help to get it on and off. A good shirt and/or suit, especially multiple ply and/or canvas material, can give a lifter a two to three hundred pound bump in a top lift. In fact, some of these shirts are so ridiculous people have to actively train doing a back row with hundreds of pounds to pull it against the resistance to touch the bar to the chest, and some suits cannot reach parallel without enough weight to push against the resistance. But given everyone can use it, it's not "cheating". And at the end of the day the shirt doesn't do the lifting. It does however expose the lifter to other risks - we're starting to wonder as people now complete over 1000lb in the bench press what the limit is before forearm bones snap.
Whereas the IPF is also extremely strict about anti-doping, other federations are not, and some of them are pretty much sports entertainment, with rampant steroid use and multiple canvas equipment to just tack on raw poundage.
The joke about powerlifters is that their gym bags are bigger than army duffel bags, and requires a certain level of strength to drag into the gym from the pickup truck. In addition to singlet and/or T-shirt and shorts, the lifter usually brings a selection of wraps, possibly shirts and suits, and/or other ancillary equipment. Because lifts are usually constrained by the ability to complete the bottom most part of the lift, many powerlifters use chains hanging from the bar (as the bar is at the lowest part of the lift, enough of the chain rests on the floor to significantly lighten the load) or thick, industrial sized rubber bands to either increase tension as the bar is pushed upwards (e.g. one end attached to barbell, other end tied to floor - as the bar pushes upwards you must resist the rubber band) or to decrease tension as the bar goes downwards (e.g. one end attached to barbell, the other to the ceiling, as the bar comes down the band takes some of the load). It can be gadget city, with the latest craze being the SlingShot, a thick band of polyester that is pulled up over the upper arms and stretches across the chest to give a similar support to the bench press as a bench shirt. The best place to get powerlifting equipment is Dave Tate's eliteFTS, and Dave is a standup real sweetheart kind of guy.
Strangely enough the idea of a powerlifting shoe hasn't taken off to the degree you would think. Chuck Taylors, being a flat canvas shoe were very popular for a while, and given that the closer your feet are to the ground the better your deadlift, ballet slippers are often repurposed for that portion of the competition (but black, never pink.)
One of the first gyms to really think through periodization was Louie Simmons and his Westside Barbell. An innovator in many ways, he came up with the idea of always lifting as heavy as possible in the Bulgarian style, but mixing up the lifts so as not to tax out the central nervous system. For example, for two weeks you bench press, then switch to decline bench press (bottom of bench raised, head downards), then incline bench press (top of bench raised, upper body at 45 degree angle), board press (bench pressing with two or more 2x4s on your chest to limit the range of motion), floor press (benching but lying on the floor) , before going back to bench. He also invented the reverse hyperextension machine, which he used to rehabilitate a broken back. Whereas most people hyperextend, putting their lower bodies on a bench face downwards and swinging the torso and head to straight and parallel to the floor by raising the torso - he invented a machine that has the upper body parallel to the floor, and weight attached to the ankles, raising the ankles until the body is straight and parallel to the floor. It's a fantastic exercise for the deadlift and squat.
Jim Wendler, a EliteFTS alum, designed a system he called 5/3/1, doing a multiple cycle "wave" of lifts either doing maximum sets of five, maximum sets of three, or maximum sets of one. It's the latest in thing in powerlifting, and is a very successful program.
It's kind of a macho sport, with T-shirts with pitbulls on them, that "LET THE BODIES HIT THE FLOOR" song screaming out, death metal, big sweaty men in beanies glowering from underneath their hats pulled over their eyes. Elite powerlifters are generally built like tanks, the stress of maximal lifting in terms of pure limit strength putting significant size on them. But there's generally less attitude than you'd think, with most of the sport's ambassadors being genuinely personable.