So, here's what you gotta do: press and hold the power button and the volume-down button at the same time. It's that simple! Your Pixel will take a screenshot, and you'll see a thumbnail of the image appear on the screen.
From there, you can share the screenshot with your friends or edit it to add some funny captions or annotations. The Pixel's built-in editing tools are pretty sweet, and you can even crop or resize the image to your heart's content.