Masturbation is NOT unhealthy. It is one way that people express and explore their sexual feelings. Masturbation is when you touch or stroke your genitals to become aroused. Girls may touch their clitoris. Guys may touch their penis.
Different people find different things erotic. Exploring your own body through masturbation can be a good way to find out about your sexual feelings and your body.
Masturbation is not bad for you. It's your choice whether you do it or not.