Microsoft Graph API gives access to data in M365. It is protected by Azure AD and thus requires you to have an access token to access the data. Here is a few steps to get started in playground.
- Go to https://aka.ms/ge to open Graph Explorer.
- Sign in with your account and start playing around with the samples in the Sample requests section.
Once ready to start building your apps. You will need to register an app with Azure AD and add the permissions for the data that you would like your app to access through. Here are a few points to consider.
- If users will login through your app and grant permissions so that you(your app) can access data on their behalf, you will need to follow Get access on behalf of a user
- If your app will not need user interaction for example running on server side environment, then you can get started with Get access without a user
You can also check Microsoft Graph Quick Start Gallery where you can kick start a sample app in your desired language and get going.