coffee machine

Also known as a coffee maker: a device that makes coffee.

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Terse, isn't it ? Let us now go into more, painful, detail.

There are many kinds of coffee makers, depending on the type of coffee you want to make. Some types of coffee (like turkish coffee) are made in ways that are so simple that a "maker" is not really necessary, although probably some technogeek is fiddling right now with an ASIC, a pot, and finely ground coffee dust.

Drip

The american classic. It operates by slowly dripping boiling water on medium ground coffee, in a paper or metal filter. The water (now turned into coffee) seeps through the coffee grounds, and drips into a pot.
It exists in many forms, from your friendly Mr. Coffee device to stainless-steel, multi-head beasts, usually found in diners or mental health institutions like universities.
The great enemy of this kind of coffee is the hot plate: in stupid coffee machines it can overheat the coffee and make it boil, which destroys the flavor.
Some of these coffee makers are fitted with a red tap for drawing boiling water. The tap usually has dire safety warnings, and believe me they are necessary.

Really heavy duty ones are connected to a water pipe, so they never need to be refilled.
With this kind of coffee makers all sorts of social badness is possible, like stealing the first cup and taking the last cup and not making any more coffee.
It is worth remembering that the first cup contains most of the caffeine ...

Percolator

This device recirculates the coffee over the grounds. Over and over. The water is kept near boiling temperature.
This destroys the taste in two ways:

1. It extracts undesirable shit from the grounds (after some hours everything will pass into solution.
2. By keeping the coffee very hot, it forces the flavorful fraction to evaporate.

Avoid the percolator.

Espresso

Born in Italy, this coffee machine operates by forcing boiling water through fine coffee dust, usually packed into a pressure-tight filter. The water goes very rapidly through the coffee, propelled by six to nine bars of steam or, in some cases, by an electric pump.
They are usually expensive and somewhat fiddly. Home versions exist, but bars and restaurants use multi-head, gas powered machines which are fired up in the morning and left under steam (think of a locomotive).
The home version usually takes longer to produce an espresso, because it has to reach its working pressure - which can take some time. The coffee produced is usually quite strong, and drunk in small amounts. Strangely enough, a standard espresso has less caffeine than a cup of drip coffee.
Usually a fitting for extracting steam and making cappuccino is provided.

A quick, motivated, coffee dude can keep an eight head machine completely busy (of course, this would not be your tipical Slobozian Starbuck's underpaid college student). If you want to see really fast espresso making, go to Milan and have an espresso close to the Stock Exchange. But don't dawdle, 'cause the brokers are even faster than the coffee dude.

Moka

The smaller brother (some might say, far removed cousin) of the Espresso coffee maker, this is invariably for home use.
Consisting of two parts and a filter, usually made with aluminum or steel (more expensive), this coffee maker is put on a gas range. The bottom part contains the water, the top part receives the coffee and between the two goes a reusable filter with tiny holes: when the water in the bottom part boils, the resulting steam pressure forces the boiling water through the coffee dust, producing a reasonable approximation of espresso.
This is the standard issue home coffee maker of Italy, the best brand being without doubt Bialetti.

One fine trick is to mix one or two teaspoons of cocoa dust with the coffee grounds. The result is very smooth and tasty.

French Press

A curious device that, through the use of a moveable filter that looks like a piston, allows the user to make coffee as if it were tea, that is to say, by infusion.
A good one is made by Bodum. The only question is, how many glass jars have you already gone through. There is a good writeup about it.

I had always assumed that coffeemakers had some sort of a heating element and a small water pump to force the water through the coffee grounds.

I was sadly mistaken.

Being a college student with far too much time on my hands, I decided to take my trusty $9 Wal-Mart cofeemaker apart to find out for sure.

It turns out that when you pour the water into the water compartment, it goes to the bottom of the machine, directly beneath the hot plate part. As you might expect, on the underside of the hot plate is a heating element. What surprised me is that on the other side of this heating element (just beneath it) is an aluminum tube connected directly to the water compartment on one end and running to the top of the machine on the other.

When you flip the switch on, the heating element gets hot, and the water flows into the aluminum tube with the help of gravity. When the water gets hot enough, it boils up through the tube towards the top of the machine. When it gets there, it just drips down through the coffee grounds and into the pot where it is kept warm until the coffee is served.

Pretty cool, huh? Water gets pumped through the machine, all without a single moving part! Except, of course, for the valve that prevents the boiling water from flowing back into the cold water compartment.