Google officially brought multi-window functionality to Android with Nougat. It was the first uniform implementation of this feature that had existed on Android in different forms and manifestations prior to Nougat. There is one major limitation, though. Apps can be opened in split-screen but Android doesn’t run the two apps simultaneously. This will change with a new feature called “Multi-Resume” which will come with Android Q.
As smartphone displays have become larger, they’re more than capable of allowing users to have two apps open at once. Android lets them do this but even though it allows for two apps to be on the screen at the same time, it actually retains one as active and pauses the other one.