Microsoft Graph API

Use the Microsoft Graph API to quickly build apps that connect to a wealth of resources, relationships, and intelligence, all through a single endpoint: https://graph.microsoft.com. For example, you can build custom dashboards, workflows, and apps that retrieve data for your organization. For more information, see the Microsoft Graph documentation.

Snippet from Wikipedia: Microsoft Graph

Microsoft Graph is a Microsoft developer platform that connects multiple services and devices. Initially released in 2015, the Microsoft Graph builds on Office 365 APIs and allows developers to integrate their services with Microsoft products, including Windows, Office 365, and Azure. At its Build 2017 conference, Microsoft announced it would use the Microsoft Graph to bring new functionality and connectivity between Windows and other OS platforms, including Android and iOS.

Office 365 Navigator - ALMBoK.com