To Take Screenshot of Whole Screen:
If you want to capture whole screen, press the following three keys together
Command Key
Shift Key
3
The screenshot will be captured and the image will be available on your Screen.
To Take Screenshot of Selection
If you want to capture only a part of your screen, then press the following three keys together
Command Key
Shift Key and
4
A selection image will appear on screen. Just drag it across your desired area , Image will be created on your Mac Screen.