In chess, castling involves the rook and which other piece?

Question

FIDE organised an international championship first held in 2019, followed by an Intercontinental Online Chess Championship in 2021 and onwards, for whom?

Answer 1

Castling is a move in the game of chess involving a player's king and either of the player's original rooks. It is the only move in chess in which a player moves two pieces in the same move, and it is the only move aside from the knight's move where a piece can be said to "jump over" another.