ACLs are Access Control Lists. These are used to set a list of rules that specifies which users or systems are granted or denied access to a particular object or system resource.
There are different types of ACLs including:
File system ACLs manage access to files and directories
Networking ACLs manage network access by providing instructions to network switches and routers that specify the types of traffic that are allowed to interface with the network.
For example. Let’s say I’m a manager and i don’t want my accountant to have control over the files that my assistant manager does; I would set an ACL for that specific directory or object for that occasion.