Someone who is new to the Internet or new to computers in general. "Newbie" is sort of a derogatory term, but hey, it doesn't have to be :^) Everybody on the Internet was a newbie once, yet many netizens tend to forget this. So, newbies are often picked on. The best way for a newbie to avoid feeling inferior for instance, is to be sensitive to the informal rules and netiquette of the net.
Now, having said that, the classic definition of a "newbie" or a "newb" is someone that is new to a game or program (or the Internet). They do not fully understand the functions of the program, however, with time and effort, the newb can grow accustomed to the software and be an active and learned user. This is very much different from a noob (n00b, nub, no0blet). Noobs are, in short, jerks, who spend their time trying to flame others because they think they are above everyone and automatically know how to do everything without ever having touched the software. No one is a pro upon beginning an activity, you have to adjust to it. Noobs fail too see this.
Even though pronounced the same, the terms "newb" and "noob" are entirely different. Many people who get on the Internet often and/or play extensive online gaming believe that being called a "noob" is truly derogatory so it is important to know this difference.
One thing to know: If you're an AOLuser and that's how you've connected to the Internet, the aol.com domain name that gets tagged at the end of your newsgrouppostings and appears at the end of your e-mailaddress will instantly identify you as a possible newbie (even if you've been on the Web for a long time now it carries that stigma). Newbies can become an online nuisance when they do not lurk, when they ignore FAQs, and when they don't take time to RTM.