Taking a screenshot on a Mac is super easy! Here's how you can do it:

For the entire screen:

Press Command (⌘) + Shift + 3.
The screenshot will automatically be saved onto your desktop.

For a specific area:

Press Command (⌘) + Shift + 4.
Your cursor will turn into a crosshair. Click and drag to select the area you want to capture.
Let go of the mouse or trackpad, and it will save to your desktop.

To capture a window:

Hit Command ⌘ + Shift + 4 and tap the Spacebar.
Your cursor will now be a camera icon. Move it over the window you wish to capture and click.
The screenshot will save to your desktop.

Finally:

If you are using macOS Mojave or later, you can press ⌘ + Shift + 5 to open a screenshot menu where you can capture the entire screen, a window, or a selected portion of it. You can even record your screen!

Let me know if you need help with anything else!