What are ‘first serve’ and ‘second serve’ in tennis?

In tennis, there is a specified boundary marked on the court behind which the ball should fall as a player serves. So, if the ball hits the net and falls back to the server’s court or goes beyond the marked boundary on the opponent’s court, it is a wrong serve. As a rule, a player is allowed to serve again if the ‘first serve’ is wrong; this serve is called ‘second serve’. If both the first and second serves are wrong, it’s a double fault and the point is given to the opponent.