What are all the AppX entries under HKCU\Software\Classes?

If you poke around in the Registry a bit, you'll find a lot of weirdly-named entries under HKCU\Software\Classes that start with AppX. They represent Windows Store apps, and you can see which entry is which by looking at the ApplicationName entry under the Application subkey.

There was some confusion over the purpose of these keys and whether they indicated a virus, so I wrote this to hopefully turn up in the search results to answer that question if other people have it.