Could someone please tell me what the difference is between "enterprise application" and "app registration" in Azure.
Appreciate if you could give me an example & why some application cannot be registered under blade "Enterprise application" and vise versa.
An App Registration is a way of reserving your app and URL with Azure AD, allowing it to communicate with Azure AD, hooking up your reply urls, and enabling AAD services on it. When you have an application that you are developing and want to integrate with Azure, you need to register your application in App Registrations, where you will configure your reply URL, logout URL, and API access if needed. When you register your application, Azure AD assigns a unique Application ID to it and allows you to add certain capabilities such as credentials, permissions, and sign-ons. The default settings allow only users from the tenant under which your app is registered to sign into your application.
The Enterprise Applications blade might be confused with App Registrations because the Enterprise Application blade contains the list of your service principals. However, the term Enterprise App generally refers to applications published by other companies in the AAD gallery that can be used within your organization. For example, if you want to integrate Facebook and manage SSO within your organization, you can integrate it from the Enterprise Applications dropdown in the applications blade. Your own applications will also be represented in the Enterprise Applications blade as Service Principals, which are instantiations of your applications in the tenant.
App Registration: https://learn.microsoft.com/en-us/azure/active-directory/develop/quickstart-v1-add-azure-ad-app
Integrating an Enterprise application (G-Suite): https://learn.microsoft.com/en-us/azure/active-directory/saas-apps/google-apps-tutorial