I used to drink these in Taiwan, Hong Kong, Japan and Los Angeles. It's coffee made by expanding water vapors and then some vaccum process that occurs when the water cools. The coffee never boils thus it tastes amazing. Now, I am jones-ing it, BIG TIME.

Almost everything about using a siphon coffee maker is sensory involved: aromas, fragrance, motion, touch, action. Grind the coffee, add it to the top vessel. Add cold (or hot) water to the bottom. Put the bottom on a heat source. Add the top vessel with its attached siphon. Watch. Liquids defy gravity. The brew gurgles, but it's not boiling. Remove from heat source. Watch the coffee move back down, or "south". Watch the bottom vessel's brewed coffee gurgle as air is drawn through the spent grounds to release the built up vacuum. Remove top vessel. Smell. Pour. Taste. Insane goodness!

CoffeeGeek.com has a great page about the entire process...

BTW, those stove top espresso makers are called macchinettas and work on a very similar process. This is a good page that explains that process well too...