yes you are absolutely right Samsung galaxy s4 is multitasking......

With Multi Window you can easily complete multiple tasks on a single screen. You can, for example, take notes or search the web while watching a movie or checking your emails. The Multi window tray has the most commonly used apps available.

Using Multi Window

1. From the Home screen, drag the Notification Panel down.
2. Then tap Multi Window.
3. Now, to start Multi Window, tap the Play icon located at the left side of the screen.
4. Tap and drag the desired app outside of the tray to open it in a Multi window screen.
5. A blue overlay will show you where the window will appear.
6. Now, with the Multi window tray open, tap and drag the desired app outside of the tray to open see it in a side-by-side view.

Tip 1: To move the location of the Multi Window tab, tap and hold the tab and then drag it to the desired location on the screen.
Tip: To switch the positions of the windows, tap and drag the header of the desired window. You can also resize the window by tapping and dragging the split bar in the middle of the screen.

Editing the Multi Window Apps

1. Open the Multi window tray and tap Edit.
2. The Multi window mode will show only the apps available in the Multi window tray.
3. While in the Edit mode you can drag add or remove icons from the tray by tapping and dragging them in or out.
4. To change the order of the icons in the tray, tap and drag the icons to the desired location.
5. When finished editing the tray, tap Done and your changes will be saved.