Buyback is a Dota 2 mechanic that lets a player pay gold to bring their hero back into the game immediately after death. Without buyback, a dead hero has to wait out the respawn timer, which grows longer as the hero's level rises and the match progresses — in the late stages of a game it can reach dozens of seconds. Buyback removes this wait entirely: the hero appears at the base right away.
The cost of a buyback depends on the hero's level and the current match time: the further the game has progressed and the higher the hero's level, the more expensive the respawn becomes. Economically, this is a significant expense — the price is often comparable to that of a major item, so the decision to buyback is always weighed against what else that gold could have bought.
When buyback decides the outcome of a fight
Buyback is most often used at critical moments: for example, when a team loses a key hero right before an important fight over Roshan (a neutral boss that grants powerful bonuses) or before an assault on the enemy's throne. Bringing a fighter back into action quickly can turn the tide of a skirmish that would otherwise be lost due to the enemy's numbers advantage.
There's also the opposite situation — a "forced" buyback, when a player is killed at an inconvenient moment, and the team critically needs that hero's presence on the map for at least another minute. In this case, the buyback isn't taken to win a specific fight, but to avoid giving up territory or a key objective to the opponent without a fight.
Tactical significance
Experienced esports teams keep track not only of their own gold but also of whether the opponent has an available buyback — this affects whether it's worth risking a new fight right after the previous one. If all of the enemy heroes have already spent their buybacks, they'll be especially vulnerable for the next few minutes, and this window is actively used to pressure the map.
The term itself comes directly from the in-game feature's English name and is used without translation — like many other Dota 2 mechanics that have become firmly embedded in gaming jargon.