Newbie is a nickname for someone who is new to something. The new guy on a team or job is a newbie. Someone who just started using the internet is a newbie. Newbies are just starting out.
This word — which has new right in it — is a slangy term for someone just starting an activity. A person on their first day at a job is a newbie. A first-time soccer player is a newbie. Freshmen are newbies. The opposite of a newbie is a veteran. Because newbies are inexperienced, they have a lot to learn. Newbies are also called rookies.