To take a screenshot on a Mac, you can follow these steps:

1. For a full-screen screenshot, press and hold down the Shift + Command (⌘) + 3 keys simultaneously. You will hear a camera shutter sound, and the screenshot will be saved as a .png file on your desktop.
2. For a selected portion of the screen, press and hold down the Shift + Command (⌘) + 4 keys simultaneously. Your cursor will change into a crosshair. Click and drag the crosshair to select the area you want to capture. Once you release the mouse button, the screenshot will be saved as a .png file on your desktop.
3. For a specific window or menu, press and hold down the Shift + Command (⌘) + 4 + Space bar keys simultaneously. Your cursor will turn into a camera icon. Move the camera icon onto the window or menu you want to capture, and click on it. The screenshot will be saved as a .png file on your desktop.

Additionally, on some Mac models, you can also use the Touch Bar to take screenshots by customizing the Control Strip, or use the Grab application (located in the Utilities folder) for more advanced screenshot options.

Remember to check your Mac’s keyboard settings, as some keys might be remapped or assigned different functions.