A n00b is leetspeek for "noob" that comes from the word "newbie" or "newcomer".
The n00b is a newbie, but unlike the Normie, they are not well-liked on the forum, possibly due to low quality posts, bad English, boasting, being a Forum Arsonist, bumping threads, not listening to advice, creating pointless threads, creating tournaments when you have no idea how to make these, lacking common sense/social skills, or really horrible bot building skill or any mixture of these. Basically just being annoying/obnoxious without contributing anything interesting. Also sometimes a Forum Arsonist, Vet Whacker or Drama Queen, though not all forum arsonists/drama queens are n00bs. Originally, the forum's n00bs were given the title "God of Shit", often in pairs. The tradition of assigning the "Two Gods of Shit" eventually depreciated and evolved into "n00b".
A person can stay a n00b for a very long time (sometimes called perman00bs), or can hopefully evolve into a Normie.
Contrarly to newb, n00b is an offensive term/insult.
It is told that you can kill n00bs most effectively through n00b whacking, but results so far have been mixed.
This word has since been deprecated and isn't used as often as it was in the past, but the concept lives on in that some users are regarded as not listening, not being good users, et cetera.