Drinking games are games which involve drinking alcoholic beverages. The point is either simply to drink, or to make your opponent drink more than you do, so that they become drunk and drink even more, and so forth.
What are some common drinking games?
Numerous drinking games based on popular television shows and genres exist; the rules for these usually instruct the players to drink when some event (such as a character speaking a catch phrase in comedies, or the use or mention of a particular technology in science fiction ) occurs, typically with the size of the drink inversely proportional to the frequency of the event - an event that happens rarely can call for finishing one's current can/bottle.
There are also drinking games that can be played with cards:
Asshole, Sheps Deal, Drink your face off, Kings Cup, Hi-Lo...