A user is an agent, either human (end-user) or software, who uses a computer or network service. A user often has a user account and is identified by a username (also user name), screen name (also screenname), nickname (also nick), or handle, which is derived from the identical Citizen’s Band radio term.
Users are also widely characterized as the class of people that use a system without complete technical expertise required to understand the system fully. In hacker-related contexts, such users are also divided into lusers and power users. Both are terms of degradation, but the latter connotes a “know-it-all” attitude.
In projects in which the actor of the system is another system or a software agent, it is quite possible that there is no end-user for the system. In this case, the end-users for the system would be indirect end-users.[clarification needed