Microsoft API is one endpoint solution to access the Office 365 services like mails, calendars and .etc. By using the graph api, no more obtaining separate tokens for different services or calling a different endpoint for each API.
Some features may be available on the individual service endpoints,
but not yet on Microsoft Graph. We are working hard to bridge these
gaps. If you require one of these features, you can use the individual
endpoint in the meantime. Check the release notes for details on the
Microsoft Graph features in preview and generally available.
For details, you could refer the document Choosing your API endpoint.
