Masturbation is giving oneself sexual pleasure by stimulating the genitals. When you keep going you will probably get more and more excited and may eventually climax. Some people just concentrate on the pleasurable feelings themselves, while others need fantasies to have an orgasm.

Is it normal to masturbate?
Why do people masturbate?
How do girls masturbate?
How do guys masturbate?

When I have masturbated I feel guilty afterwards.