Apps for websites is a feature that uses web-to-app linking to associate an app with a website.
Apps for websites was first introduced in Windows 10 build 14342, but there were no apps available at the time that supported this.
Starting with Windows 10 build 15007, clicking links to websites that support web-to-app linking will now open that page in the respective app. You can now also turn on or off open sites in apps for Microsoft Edge.
This tutorial will show you how to turn on or off the open sites in apps feature in Microsoft Edge for your account in Windows 10.