It is called a fault or if you do it again it is called a double fault.
There ISN'T anything called a "backhand serve" in tennis.
It is called a service ace!
If the player is unable to hit the serve then it is an ace. But if the player hits the ball but does not return it, then it is a forced error.
Because you hit the ball with some kind of racket and that is why you call it a serve.
The server has two chances.
Although personal style and flair play a small role in serving, the proper way to serve a tennis ball is too long to describe on this website. Instead, click on the wikiHow link, below, for detailed instructions.