They can kiss, touch each other's bodies, suck on each other's nipples or play with them with their hands. They can also use their fingers to rub the person's vagina (for a girl) or penis (for a guy), or stroke their anus if they want to be extra gross about it. Sometimes people like to put their private parts inside another person's mouth, vagina, or anus. There are lots of different things people can do during sex, but those are some of the basics.