Currently, if you're a software developer and want to create an app, you have to write the same program multiple times. Once for Android, once for iOS, maybe once in Chrome (although it looks like ChromeOS will be able to run Android apps soon), and once in HTML for desktop dinosaurs like me. Lots of developers skip that last one, locking desktop users out of their product. This situation profoundly annoys me, and I assume iit annoys lots of other folks too. Not just being unable to use an app if the developer didn't bother with my platform, but as a developer myself I find the redundant effort offensive.
The W3C has been defining a lot of new APIs for use in web pages. You can see a list of all the APIs here: https://www.w3.org/standards/techs/js. I made a few pages to demonstrate some of the APIs. They are directly applicable to writing web apps.
Draft APIs, probably not available yet:
You are welcome to View Source and copy code.
ACME Labs / Web APIs