S&M is sadomasochism. Some people get sexual emjoyment out of inflicting physical or mental pain on their partners, or receiving it themselves. This is not the same as abuse. In abuse, one partner does not consent. In S&M, both partners want it.
It's both fine and normal to rub your clitoris to orgasm. That's usually how I do it too

If I only fingered my vagina I wouldn't climax.