When permissions are applied to a file or directory, they are applied at three specific levels: owner, group, and world.
The user (sometimes called owner) permissions simply control what permissions the file owner has.
Group permissions determine what actions can be performed by members of the same group to which the file belongs. Your system administrator can create new groups, or add you as a member of a group.
Other (sometimes called world) permissions are for a huge group that encompasses all the users on your computer. For example, email-related directories often assume other permissions.
If there is guest access to your computer, you can assume that any active other permissions apply to anyone who can access your computer. ...