Google is working on improving the User Experience of Android with a new Multi-Window tool that will be included on the Android L official release, which is by the way pretty soon (October 16th).
Basically, users can have two open apps at a time. From the recents app menu, users could swipe recent entries to either side of the display, "snapping" them to that half of the screen, leaving the other half of the screen occupied by the home screen or recents app menu.
Samsung already included this feature with the Samsung Note 3 TouchWiz UI, Google took the same concept but made it a lot easier to push an App to fir half of the deices's screen. We should see this feature as a default on all Android L devices.