When you stay in one place not doing much of anything in particular, you hang around. If you've got a half hour between classes, you might hang around talking to friends or eating the apple from your lunch.
There are a lot of ways to say hang around, including loiter, dawdle, hang out, and lollygag. If you walk through any shopping mall or public park, you'll see many people who like to hang around there. Sometimes this verb means "associate with," so your grandma might ask, "Why do you hang around with those kids who have strange haircuts?" This phrase dates from the early nineteenth century.