As a SharePoint Online admin, you can create an App Catalog site to make internally developed custom apps available for users to install when they browse apps under the From Your Organization filter on the Site Contents page. Site owners can then add these apps to customize sites with specific functionality or to display information.
After an App Catalog site has been created, you can use it to upload any custom apps that your organization has developed. Uploading custom apps isn’t much more complicated than uploading a document to a library and setting some properties. You can use the App Catalog site to do things like install custom or third-party apps on sites for users (also called app deployment). You can also manage app requests from users.