Dota 2 calls its player-controlled characters heroes.
The terminology comes from Defense of the Ancients, the Warcraft III custom map that inspired Valve’s standalone sequel. Each player selects one hero and controls that character throughout a match, using abilities, attacks, items, and movement to help the team destroy the opposing Ancient.
A standard Dota 2 match has two teams of five, so ten players control ten heroes. Heroes differ in attributes, abilities, strengths, and intended roles. Some are cores that scale strongly with items and experience; others are supports that provide vision, healing, disables, buffs, or protection.
The distractors reflect terminology from other games. League of Legends uses “champions,” while “agents” is strongly associated with games such as Valorant and “operators” appears in other tactical shooters. Dota 2 does contain computer-controlled creeps and neutral units, but those are not the characters selected and directly controlled by players. The canonical Dota term is heroes.