Okay. Mr. pihwlook did a pretty decent job of describing what BCT is like from a simple overview, but there's a little more to it than that. Let me give you a brief look inside of basic training at Fort Sill, Oklahoma (which I couldn't help but notice was left out of the major training sites):
The first few weeks were the worst. I knew practically nothing about the military prior to enlisting. Nothing about rank structure. Nothing about military history. Not even the difference between an officer and an NCO (non-commissioned officer). Nada. So, as you can imagine, I was already trying to ice skate uphill.
As has been mentioned above, BCT is roughly divided into three phases: red, white and blue. Each lasts approximately three weeks, and more 'freedom' (read: basic human rights) is given to you at each phase. Not that you can really notice any difference; the different phases really just serve as reminders that you are making progress, and not trapped in purgatory for all eternity. And not a nice purgatory. This is a purgatory where angry men with personality disorders hold absolute power over you. And they do not like you.
Ahem. Sorry, PTSD kicked in there. But seriously, most of basic is like a stretched-out, very painful root canal. It sucks, seems to last forever, but often gives you interesting stories to tell later. For example, we were out at the rifle range one day towards the end of basic. We were very strongly cautioned to keep our weapons aimed downrange, since nobody wanted an accident. Of course, somebody had to screw it up. We were in our firing postions inside of sunken concrete tubes, which were appx. three feet across and five feet deep. The soldier in question turned to ask the drill sergeant something, apparently forgetting that he had a loaded weapon with the safety off pointing at the drill sergeant's face. About three minutes later, two other drill sergeants were able to pull the first off of the now-severely beaten soldier. What happened? The drill sergeant (DS B. for short) jumped into the tube with the soldier, grabbed him by collar and belt, and began hammering him against the concrete walls. Fortunately, the foolish bastard was wearing his helmet, and was able to stagger away with no major injuries.
Similar incidents occured, of course. Now, drill sergeants aren't directly allowed to injure you anymore. They will, of course. They're just more creative about it. They can either make you hurt yourself through intense physical fitness training, or "teach you about applied self-defense". These were both favorites of my platoon drill sergeant, a black belt in aikido. The latter usually consisted of him picking a soldier who had been pissing him off, and then proceeding to throw said soldier around like a rag doll until he was tired of it.
Now, add in sleep deprivation, intense physical and emotional stressors ( bad food, constant physical exercise, bad men yelling at you, 108 degree weather) and you might have some inkling of what a "good" basic training experience is like.
Of course, there is a continuing trend these days to "integrate" male and female BCT programs, and there is a lot of contreversy over it. Most males that have been through it complain that it felt too "watered-down" or was run at too slow of a physical pace to challenge them. Or, if you prefer to experience it yourself, we're always hiring :) Just ask for Fort Sill or Fort Benning if you want a "real" basic training experience.