Games are a billion-dollar industry and a big part of the animation business. Almost every game has animation in one form or another, and most of that animation is in 3D. Animating for a game is very much like animating for film or video, but with a few restrictions.
First, because games happen in real time, This puts a huge demand on the console to render scenes in real time. To accommodate this, most characters are limited in the amount of detail they have. Deformations can also be difficult to compute in real time, so most games do not incorporate features such as dialog with accurate lip-sync. These limitations will certainly fade away in the future as consoles get more powerful.
Animating for Games
Creating animation for games is fairly straightforward. The big difference is that, outside the cut scenes between game levels, you rarely animate anything straight through. All animation in a game is comprised of short cycles and moves that are strung together to make continuous animation.