Keyboard shortcuts are used to save time, and keep you from having to go back and forth between the mouse and the keyboard. Your Chromebook recognizes a lot of different shortcuts! To see them all click Ctrl + Alt + ? and a pop up screen will appear that will let you see all of your options as you press different buttons.
If you're just looking for something fast, and don't have time to explore all of your options right now, the chart below is from Google and displays some of the most common keyboard shortcuts (according to the Google Chromebook Support forum).