Let's Talk About Azure Active Directory and the Microsoft Identity Platform

Matthew Levy - thanks for the question! 

The way I like to think about it is that each Azure AD application models a "real-world" application. Each AD app is going to have attributes specific to that real-world application. Like reply url, client secrets, or even API dependencies. (The latter 2 of which I'll get into in a subsequent article.)

So if the application gets deployed distinctly / offers a distinct set of functionality ... then it probably should have its own Azure AD application. (Although a case can be made for a web app & a mobile app to share the same AD application.)

Hope that helps.