Unix/Linux permissions can be a confusing thing so here is a full explanation on how they work and how they differ on Unix servers.
The basic unix permissions come in three flavors;
Owner Permissions : These are permissions that you have on your own files or directories.
Group Permissions : These are permissions that you and anyone in your group have on the file files or directories.
Other Permissions : These are permissions that other people have on your files or directories if not you, or in your group
So, in Unix, when permissions are configured, the server allows you to define different permissions for each these three different categories of users. In a Web Serving environment these permissions are used to control which website owners can access which directories and files.