Is Microsoft Graph an API?

Yes, Microsoft Graph is an API. More specifically, it is a single, unified RESTful web API gateway that allows developers to access data and intelligence across various Microsoft Cloud services. 

Instead of interacting with individual, separate APIs for different Microsoft tools, you can use the unified Microsoft Graph API endpoint (https://graph.microsoft.com) to communicate with multiple services simultaneously. 

What It Connects

Through Microsoft Graph, you can interact with a wide range of data points, including: 

Microsoft 365 services: Outlook/Exchange, OneDrive, SharePoint, Teams, Excel, Planner, and OneNote.
Identity and Security services: Microsoft Entra ID (formerly Azure Active Directory) and Intune.
Windows services: Devices, notifications, and activities.

Why Is It Called a "Graph"?

The name comes from data science terminology rather than visual charts. In tech, a "graph" is a network of data points (nodes) and the connections (edges) between them. Microsoft Graph maps out the relationships between different entities—such as a user, their manager, the files they recently edited, and the meetings on their calendar—making it easier to fetch contextual, interconnected information. 

Typical Use Cases

Developers use the Microsoft Graph API to automate tasks and build intelligent applications, such as: 

Creating new user accounts or managing permissions.
Reading calendar availability to automate meeting bookings.
Sending emails or posting automated notifications to Teams channels.
Accessing files stored in OneDrive to analyze data. 

If you want to experiment with how it works without writing code, Microsoft provides a free web-based playground called the Microsoft Graph Explorer where you can test live API requests and view sample data.