Banned Deviants are the counterpart to Deactivated Accounts, with the likeness being that their username is crossed out. Before being banned, a Deviant would have to cause several small violations to the ToS or some rather large violations in order to be removed from site. Once banned, you may apply for a Ban Appeal, but only in very rare cases are Deviants let off with this. Once banned, the user are blocked from commenting, favouriting, uploading, chatting, posting on the forums, starting forum threads, giving badges, joining groups, creating groups, voting on polls, writing journals, buying points, spending points, donating points, giving critiques and several other main site features. You are still able to log into your account and check your messages, normally Deviation stacks.
Bans are the permanent versions of Suspensions. Although it is usually against the policies, these are usually worked around with a sockpuppet.
A Picture of a User that got banned on deviantart:
for example: This user which is named "Magic-Monkey 761" got banned for spamming on Deviantart