Films and games are both thought of as a visual medium, but the reality is that sound plays almost as important a part in the final product. In addition to tackling every piece of music within a game, a sound designer/engineer must also track down (and usually must record) every sound effect, piece of dialogue, and ambient sound within the game (this includes wind, water, city street, and so on). These are pretty much the same assets for which a sound designer would be responsible when making a movie. Because of this, many sound designers have worked in both areas, games and movies, as well as applying their trade to theatre productions and television.
Excluding the music, the sounds that you will import into the game will either ...