# Working modes overview
App Ops has four working modes, each with the same effect (except multi-user support), but not the requirements and setup process.
If a work mode supports multi-user, you can manage other users from App Ops installed on the primary user, otherwise you will need to install App Ops on each user.
Android Debug Bridge (adb) is a versatile command-line tool that lets you communicate with a device. The adb command facilitates a variety of device actions, such as installing and debugging apps, and it provides access to a Unix shell that you can use to run a variety of commands on a device. Some working modes require the use of adb.