Windows 8 Snap
Windows 8 apps normally run full screen, but you can run two of them side by side using a feature that Microsoft calls Snap. With both apps running, mouse over the upper-left hot corne and move your pointer down. Click and hold the thumbnail of the app you want to run beside the current one, drag the thumbnail to the right and drop it.
The two apps will now be running side by side, with the one you just dragged appearing in a sidebar on the left. To resize the two app panes, drag the border with three dots on it to the left or right.