I have been playing with some of the apps, while they are still working, and noticed some things that may or may not been discussed.
OK, you can open an app and it will go full screen. So it is obviously open. You can go to the desktop, or another app and the previous app will remain open...
appappstatus
desktop
full screen
functionality
live tiles
metro ui
multitasking
navigation
observation
operating system
system behavior
task management
tile management
user experience
user interface
weather app
windows 10
windows key