As clever as computers are, they still need us to tell them exactly what to do. These special settings or 'permissions' are like a sticky label on the file which your webspace will be able to read. This label gives your webspace special notes about the file and how it should be treated. These labels normally say one of the following to your webspace: "This is a normal webpage - just show it to the surfers." "This is a special file that you can add information to." "This file is a computer program - run it!" Whenever you create and upload a file (say index.html of your website) it will get a regular label slapped on it automatically which tells the server "This is a normal webpage - just show it to the surfers."
A set of conventions for controlling access to a file. A file's permissions consist of access modes and deny modes.
When you place files on a UNIX system you can assign the files various levels of permission, specifying who can access them, and what type of access they can have.