OneDrive Files On-Demand helps you access all your files in OneDrive without having to download all of them and use storage space on your device. Files On-Demand is included with the latest Windows 10 Fall Creators Update - a free update to Windows 10.
Files On-Demand works with all the apps you use today, including Windows desktop apps and apps from the Windows Store. Furthermore, Files On-Demand works with all your personal and work files from OneDrive and SharePoint Online team sites.
Learn more about Files On-Demand on this web page; which includes a short explanatory video.