Let first service mean in tennis is a rule that requires the player to serve first. The server must hit the ball over the net and into his opponent’s court, after which either player may return it back across the net. If this does not happen, then a point is awarded to the server. In singles play, each player has two chances to get their serve in; doubles players have only one chance each. This rule helps ensure fairness as it prevents any one person from dominating long rallies by continually serving without having to face an opposing return of shot. It also encourages aggressive play and strategy - since whoever serves first holds an advantage with regards positioning on subsequent shots - leading to more exciting matches for spectators and viewers alike!