For a file or folder, the three basic types of users are:
Owner - The user who owns the file or folder. Only a system administrator (root user) can change the owner of a file or folder.
Group - Users who have been grouped together by the system administrator. For example, the members of a department might belong to the same group. This group is the owning group and usually includes the file or folder's owner.
Other - All other users on the system besides the owner and owning group.