A buff is an increase to the power or effectiveness of a character, weapon, ability, or strategy, either as a permanent balance change in an update or as a temporary boost during play. Its opposite is a nerf.
The word comes from the older sense of buffing, polishing or strengthening, reinforced by games that use buff for a temporary beneficial spell. The two uses live side by side. Inside a fight, a support character buffs the party with a spell that raises attack or defence for a minute. Between versions, the developer buffs an underused character by improving its numbers in a patch. Context decides which meaning applies, and both mean the same direction: stronger than before.
Developer buffs follow the data in reverse of nerfs. A character nobody picks, a weapon with a poor win rate, or a strategy that loses to everything signals wasted design that a buff can rescue. Small buffs are preferred because overshooting creates the next problem: yesterday underused pick becomes today dominant one and queues for a nerf in the following patch.
Players ask for buffs to their favourites openly and treat receiving one as a small event, checking patch notes first for their character name. A well judged buff diversifies the meta by making a new option viable rather than by weakening the current one, which is why many players consider buffs the healthier tool of the two.
In play"Hoping for a buff to my main in the next patch, because nobody picks her at high rank."