https://www.techradar.com/news/microsoft-aims-to-make-progressive-web-apps-even-better-in-windows-10-redstone-5

Microsoft included support for Progressive Web Apps (PWAs) in the recently-released Windows 10 April 2018 Update, and at its Build 2018 event, the company went into more detail about how these specially-made web apps can revolutionise Windows 10 in the future.

PWAs are websites (or web apps) which are implemented as native apps, and act just like a normal app would, giving users notifications, live tiles, and even working offline in Windows 10. The idea is to encourage more companies to create these apps, and up until now they were downloaded and installed like regular Windows 10 apps from the Microsoft Store.