An app in Salesforce is a container for all the objects, tabs, processes, and services associated with a business function.

There are standard and custom apps that are accessed using the App menu located in the top-right corner of the Salesforce page, as shown in the following screenshot:

When users select an app from the App menu, their screen changes to present the objects associated with that app. For example, when switching from an app that contains the Campaign tab to one that does not, the Campaign tab no longer appears. This feature is applied to both standard and custom apps.