Pleasure varies from person to person. It's the stimulation of the chest and the two things near the hip and under the stomach and under the spinal chord. If your a girl. If your a guy it's playing with your churro until custard flows out of it.
It's a perfectly normal and also perfectly safe way to release sexual tension, by stimulating the genitals--the penis, if you're a boy, the clitoris and vulva if you're a girl. The important thing to know is that all those old wives tales about going blind or going crazy or, yes, silliest of all, growing hair on your palms, is so much nonsense. It's true that some religions teach that it's wrong or a sin. That's something you need to discuss with your parents, or perhaps your pastor.