Most current file systems have methods of administering permissions or access rights for specific users and groups of users. These systems control the ability of the users to view or modify the contents of the filesystem.
Permissions on Unix-like systems are managed in three distinct classes. These classes are known as user, group, and others.
Permissions on Windows systems can be granted to users, groups, computers, or other built-in security principals such as SELF or CREATOR OWNER.
Permissions are generally configured in an Access Control List (ACL, pronounced ackle) with each entry in the list being referred to as an Access Control Entry (ACE).
