post-game analysis; post mortem
Used in board games like go, chess, and othello for the discussion after a match where players review moves and strategies.
対局後、二人は感想戦で互いの手を振り返った。
After the game, the two players reviewed each other's moves in a post-game analysis.
Compound of 感想 (impressions) and 戦 (match/game), literally 'impression match', referring to the discussion after a game.