Use the sidebar to open freeform apps in a small window that you can move and resize.
On the sidebar, tap 
Or, go to Settings > Gestures > Sidebar > 
Customise the menu:


You can show your two most recently-used apps in the sidebar. If there aren't any recent apps, you'll see two recommended apps instead.
On the sidebar, tap 
Or, go to Settings > Gestures > Sidebar.



In addition to the sidebar, you can set apps to open in freeform mode from your notifications.




If you use Gametime, it has its own sidebar menu that opens apps. You set up the apps for that menu separately.