You get access to the forums. That's all. The rest of this site is free.
The only reason why I make anyone join is because of U.S. law: no pre-teen may legally join without parental consent
. So, if you are under 13, please get your parent's consent. But, for now, there seems to be no reason for a pre-teen to join. Someday, when there are discussion forums for students, I will block access by having people subscribe with a credit card for free. No one under 18 can get a credit card.
An adult parent or guardian can register his child as a member, as well as joining himself. Just register twice.