The Apps settings is the central area within an Android device where you can definitively list all apps installed on your system, as well as information about them such as the storage space and data they have used, their permissions and any default actions set. You are also able to uninstall apps (or just disable them) and manipulate their permissions and defaults.
Note: while you can also view a list of apps within the Play store, that list won't include any apps you have installed that did not come from the Play store, and cannot list system apps.
The main section of the Apps settings screen shows a list of the apps installed on your system. By default, it will list all apps except system apps, which will include both apps you have installed yourself, and any non-system apps that were pre-loaded on your device. System apps may be shown by selecting Show system from the overflow (three dots) menu.