The first question is, What is Azure AD? So, the most important thing to understand about Azure AD is that it is not a replacement for your on-premises Windows Active Directory.
In fact, it is designed for internet scale and internet-based standards and protocols. So when you walk into work every morning, and you log on to your Windows computer typically on a domain, Azure AD does not change that. You’ll still use Windows Active Directory to manage PCs, mailboxes, groups, users, etc. Azure AD is more aimed towards internet scale, internet-based standards, protocols, and applications targeting cloud-based applications.
WebHooks are user-defined HTTP callbacks. The problem they intend to solve is “pushing” information to you. Pushing is an unusually complex problem to solve. We’ve gotten so used to server-based applications, such as Office 365 resources, to expose a REST API that you “pull” information from.
Your application makes an HTTP call to find out if there is anything new. Pull works, but has some distinct disadvantages. It’s certainly not responsive enough for real-time operations, such as chat. And more importantly, it puts an undue load on both your application and the server.
At its heart, Office365 facilitates collaboration. Sure, there are tools like Word, Excel, etc. But the bottom line is that Office365 helps you manage information, and it helps you do so between teams.
With that in mind, Microsoft introduced the concept of Office 365 Groups. A group is exactly what it sounds like: a number of people, a group, who want to work together. You create this group, and “hang” different things on the group.