Why Is There 100 By Some People's Name?

So I have been looking at some of the users lately and some of them have the number 100 in parenthensis by their name. Why is that? Is it because they have been on this site longer or are they just important people? It's really confusing and if anyone could help that would be really appreciated. Can anybody tell me how you get promoted to being on the Mibba committe because I thought like adults ran this website or is it teenagers? If you could answer any of these question they would by very heplful. Thanks and have a good day.