Are you talking about Metro apps? If so, you can have one app snapped to the side of another in Windows 8, but only if the resolution of your screen is high enough to support it. I believe the minimum resolution is 1,366 x 768.
To snap an app to one side, move the mouse pointer to the top of the screen until it turns into a hand, left-click and hold the button down, then drag the app to one side or the other and let go. You can then open another app alongside it, or you can have a Metro app snapped to one side of a desktop app (and vice versa).
Another way to do it is, if you move the mouse to the very top-left corner of the screen, then move it down, it will open a list of any apps that are open. You can then right-click on one and choose to snap it to the left or right.
Hope that helps.