Users are also widely characterized as the class of people that use a system without complete technical expertise required to fully understand the system. In most hacker-related contexts, they are also divided into lusers and power users. Both are terms of degradation, but the latter connotes a "know-it-all" attitude. See also End-user and Nomadic User.

A user account allows one to authenticate to system services. It also generally provides one with the opportunity to be authorized to access them. However, authentication does not automatically imply authorization. Once the user has logged on, the operating system will often use an identifier such as an integer to refer to them, rather than their username. On Unix systems this is called the user identifier or user id.

Computer systems are divided into two groups based on what kind of users they have:

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.