Its called a Crown. Most people have one crown, some have two. Haven't seen more than that.
How do you get rid of it?
I was just looking up this question as well cos I was wondering the same thing. My oldest child has 1, my second child has 2, my third child has 3 and my fourth child has 2. Child two and four and girls so its really annying cos the at the back of their head so they get the "alfalfa" look if it is short. The only time my third child's is annoying is when I cut his hair cos it is hard to get it all cut even around the 3 of them.