Complex sentence: Buff is a term used in some video games, especially MMORPGs and MUDs, to describe an effect (usually cast as a spell) that temporarily enhances a player.
Split into simpler sentences: Buff is a term used in some video games, especially MMORPGs and MUDs, to describe increases in the power of a game element. The second usage of buff describes an effect (usually cast as a spell) that temporarily enhances a player.