From what I understand there are 3 levels of banning:
Temp ban - a temporary ban for a given time decided by the banning mod/admin
Perma ban - a permanent ban on the users account, therefore they lose all their stats, and access to editing their media and profile
IP ban - a ban on the users IP and MAC address as well as a perma ban on their account, effectively ending the users ability to regularly log into the site (even if they create an alias)
Of course there are ways around these things...it is the internet after all. Temp and perma ban still gives users access to alias's, however it means starting over essentially. I know people who have been perma banned and just stopped coming on the site because they didn't want to bother making a new account and having to gain their reputation all over again.