Is it possible to display multiple apps on the screen?
Normally, apps load fullscreen, and app-switching switches between fullscreen apps. Is it possible for an app to use only half of the screen and another one to use the other half?
If you have a Samsung phone, there is a split screen option. I personally have not used it, so you would have to look into it. The option is not available as stand, no.
There are some third party ROMs, that are capable of doing it but you would need to root your phone. Have a look at the link below. I had a quick look out on the web and found this:
How to Get Multi-Window Multitasking on Any Android Phone or Tablet