Perma bans SERIOUS rules that you will more than likely not get unbanned for breaking, period. These are rules such as exploits,duping and combat logging (granted the other two examples are forms of exploiting but shh). Normal bans are for the 'less serious rules' however, in reality they are all serious. Normal bans don't require a cool down for 6months (unlike perma ban offences, which, you may not be unbanned for anyway)
does that clear it up? If not, what particularly confuses you? If it would be better explained by voice you can PM me or join the 'join for staff attention' room on teamspeak and a support member will assist you.