noun
sports commentator; play-by-play announcer
Refers to a person who provides live commentary during a sports event, describing the action as it happens.
彼はプロ野球の実況者として有名だ。
He is famous as a professional baseball commentator.
noun
Let's Player; game streamer
Used in gaming contexts for someone who records or streams themselves playing a game while providing live commentary. Often associated with 実況プレイ.
See also: 実況プレイ
人気の実況者が新しいゲームを配信している。
A popular Let's Player is streaming a new game.
A general term for announcer or newscaster, not limited to sports or gaming. 実況者 specifically implies live, play-by-play commentary.
Compound of 実況 (live coverage, actual situation) and 者 (person). The gaming sense is a modern extension from the sports commentary meaning.