Microsoft's Brad Anderson explained how this new agreement with Citrix  wil l work in a blog post:

As part of the expanded partnership, Microsoft and Citrix will offer customers flexible options to deploy Windows 10 Enterprise within their organizations. Later this year Citrix will offer Windows Enterprise per user customers the option to manage their Windows 10 Enterprise Current Branch for Business images on Azure through its XenDesktop VDI solution. This will help customers deploy virtual apps or desktops and, along with existing Citrix' migration services, accelerate Windows 10 adoption for those customers who are using Microsoft Cloud solutions.

Why is this important for you? This significantly reduces what has been the most expensive and time-consuming part of an enterprise deployment of Windows – app compat testing. With AppDNA and the proven virtualization capabilities of Citrix, you can confidently accelerate the move to Windows 10 for your organization. And, with the ConfigMgr integration, you can manage all apps on Windows 10 devices with a single console.

Anderson added that its Azure cloud service will be used by Citrix "for its preferred and strategic cloud for its future product roadmap."

Citrix Systems, Inc. is an American multinational software company that provides server, application and desktop virtualization, networking, software as a service, and cloud computing technologieshe company began by developing remote access products for microsoft. It licensed  from Microsoft and has been in partnership with the company throughout its history.