Masturbation
It helps you to know your own body better and learn to know what you like and what you don't like and experience the different sensations your body may feel. It is good to understand your body and know what feels good for you before you have a sexual relationship with someone as you will be able to let them know what hits the spot, or not!
Some people may start to masturbate during puberty to explore touching their own body to find out what feels good. Hormones developed in the body can make you feel horny making you want to touch yourself for pleasure.
Masturbation is NOT bad for you and it does not matter how often or how you do it.