There is a built-in overview mode on your Chromebook that lets you see every open window at a glance. If you've ever used a Mac, this is just like Expose. It's also just as useful!
On the top row of the keyboard, just press the ]] button (above the 6 key) or swipe down from the top with three fingers on your trackpad or touchscreen to go into the overview. Clicking any of the thumbnails will open that window, and clicking in a blank space will return you to the last window you were viewing. If you find yourself with a lot of windowed apps running all the time, this is a great time-saver.
As a bonus, while in overview mode, you can type to filter what you're seeing. For example, typing "Google" will only show windows with the word Google in the title.
Note: The above comes directly from their article. Click here to read more.