A noob is a beginner
A noob (newbie is also a widely used term) is a novice, a newcomer on a certain terrain. The term is primarily used in Internet communities or computers-related matters. In general, the term is used in a negative sense, a mild form of a swear word. It is not always meant to be negative, often giving people themselves to be a noob, so to indicate that they are very bad somewhere in, or ignorant in a certain area.