In gaming, a nerf is a change that makes something weaker, and a buff is a change that makes something stronger. These terms usually appear in balance updates and patch notes.
What can be nerfed or buffed
Developers can adjust weapons, characters, abilities, items, maps, enemies, rewards, cooldowns, damage, speed, or costs. The goal is usually to make the game feel fairer or more interesting.
Why players debate balance
A nerf can frustrate players who liked the old version. A buff can make a weak option viable. In competitive games, small changes can affect the whole meta.
Nerfs and buffs are especially important in PvP games, MOBAs, shooters, gacha games, and esports.