To take a screenshot, press and hold these three keys together:
Shift, Command, and 3.
If you see a thumbnail in the corner of your screen, click it to edit the screenshot. Or wait for the screenshot to save to your desktop.
By default, screenshots save to your desktop with the name ”Screen Shot [date] at [time].png.”
In macOS Mojave or later, you can change the default location of saved screenshots from the Options menu in the Screenshot app. You can also drag the thumbnail to a folder or document.