Tempo
A tempo is one move's worth of time in a chess position.
A move gains a tempo when it improves your position while forcing the opponent to spend a move responding. Repeatedly moving the same piece without a clear reason may lose time.
3.Nc3 develops with tempo
In the Scandinavian Defense, 1.e4 d5 2.exd5 Qxd5 3.Nc3 develops White's knight and attacks Black's queen. Black must spend another move on the queen while White has improved a new piece.
Starting position · Position 0/5
A useful threat can gain a tempo
Developing a bishop while attacking the queen improves your position and may force the queen to move again. The opponent's repeated queen move is often described as losing a tempo because it delays another useful action.
Repeated moves are not automatically wasted
A second move with the same piece can be correct when it wins material, avoids a threat, or reaches a square the position now requires. Tempo describes the cost in turns; the position determines whether that cost was justified.