Female masturbation is when you're a female and you touch your own body for sexual pleasure. People usually touch their genitals, and often to the point of orgasm - though not always.
Most people masturbate to enjoy sexual pleasure and relieve sexual tension. Masturbation has physical, as well as mental, emotional, and spiritual components. It obviously involves the body, but what we think about, read, listen to, or watch while we masturbate involves the mind and our emotions too.