Chromebooks allow you to create multiple Desks, which are effectively virtual monitors, onto which you can sort multiple apps and activities. Press the key that looks like this (Switch Windows):

...or swipe up on the touchpad with three fingers at the same time. This should open the Overview:

Press the + (plus) button at the top middle of the screen to create a new desk, name it if you'd like, then click and drag a window to it:

You can create as many desks as you'd like. Quickly switch between them by swiping left or right on the touchpad with four fingers.