1. Command + Shift + 3
- press Command key + Shift key + 3
- the entire screen will be captured
- screenshot will be saved to the desktop
2. Command + Shift + 4
- press Command key + Shift key+ 4
- the cursor will become a crosshair
- the crosshair can be moved to select an area
- the highlighted area will be captured
- screenshot will be saved to the desktop
Reference: How to screenshot on Mac: All you need to know - Digital Citizen