Each file and folder/directory inside a server has its set of access permissions that is associated with it. These access permissions includes the owner of the file, the group of the file in which it is associated, and the read, write and execute permission for a file.
This will allow allow you to choose who can use, access and control them on what they wanted to do with the files or folders/directories. There are 3 groups for file access and 3 permissions for users to be used.Groups:
||Write + Execute
||Read + Execute
||Read + Write
||Read + Write + Execute