The answer is:

Tempo in chess refers to the difference in development between two players. It is a term used to describe the advantage gained by a player who makes a move that forces their opponent to respond in a way that is not ideal or desired.

Explanation:

In chess, development refers to the process of bringing your pieces into active positions on the board, such as developing your knights, bishops, and castling your king. The more developed your pieces are, the more control and influence you have over the board.

When one player gains a tempo, it means that they have made a move that not only advances their own position but also forces their opponent to respond in a way that is not as beneficial. This can be achieved by attacking an opponent's piece or creating threats that require immediate attention.

Example:

Let's say Player A moves their knight to a square that attacks Player B's queen. Player B is now forced to move their queen to a safe square, losing a move in the process. Player A has gained a tempo because they have developed their piece while also forcing their opponent to respond defensively.

Importance:

Tempo is an important concept in chess because gaining an extra move or forcing your opponent to make suboptimal moves can give you an advantage in the game. It allows you to maintain the initiative and dictate the tempo of the game. By being mindful of tempo, players can strive to make moves that not only benefit their own position but also put pressure on their opponent.

Conclusion:

In conclusion, tempo in chess refers to the advantage gained by a player who makes a move that forces their opponent to respond in a way that is not ideal. It is a concept that highlights the importance of gaining an extra move or forcing the opponent to make suboptimal moves. By understanding and utilizing tempo effectively, players can gain an advantage in the game and control the rhythm of play.