Chess endgames refer to the phase of a chess game when there are fewer pieces left on the board. This phase requires different strategies and techniques compared to the opening and middlegame. Key concepts in endgames include understanding the importance of king activity, pawn structure, and the role of pieces in converting advantages. Common endgame scenarios include king and pawn endings, rook endgames, and minor piece endgames. Mastering endgames is crucial for converting winning advantages and saving lost positions.