Tempo

A tempo is one move considered as a unit of time on the board. It does not refer to the seconds remaining on the clock. Every turn can accomplish a task, such as bringing a piece out from its starting square, creating a threat, or placing the king on a more useful square, so reaching an objective in fewer moves may be decisive.

A player gains a tempo when one move serves a purpose while also making the opponent respond. A piece might complete its development, moving out from its starting square, while attacking another piece. A tempo is lost when an extra move is needed to reach the same result, such as moving one piece twice without obtaining enough benefit.

The comparison always depends on the position. Moving a piece repeatedly is not automatically a waste if each move creates a useful threat. Likewise, forcing an enemy piece to move may bring no real gain if that piece reaches a better square. What matters is which tasks each side completes and how the initiative, the ability to connect threats that demand replies, changes.

The special endgame case

In some endgames, the phase in which few pieces remain, deliberately losing a tempo through a waiting move is correct because the opponent must then act in the critical position. This may create zugzwang, a situation in which a player must move but every legal move worsens the position. A seemingly idle move can therefore be best because it changes who must act at the decisive moment.