Gold is the in-game resource spent to buy items during a League of Legends match.
Champions use gold at their team’s shop to purchase equipment that improves attributes such as attack damage, ability power, armor, movement speed, or health. Items can dramatically change a champion’s strengths, so earning and spending gold efficiently is a major part of the game’s strategy.
Players receive some gold passively as a match progresses, but active income comes from actions such as killing minions, champions, and defensive structures. Last-hitting minions is especially important because it reliably awards gold to the champion that deals the killing blow. Teams can also gain gold through objectives and other game events.
Gold is temporary match currency: it does not carry from one game to the next. It is also different from Riot Points, a separate currency used for optional purchases such as skins and other cosmetics outside normal gameplay. Mana, meanwhile, is a resource used by many champions to cast abilities, not to purchase items.