When you boot your PC it perform first POST procedure , What does POST mean?

POST mean Power On Self Test , its a test the PC doing automatically once the Power Button pressed to test the functional of all PC equipment (RAM, processor, H.D ...) 

1. First of all POST is called Power On Self Test.

2. It is a diagnostic sequence test that a computer's I/O system are runs to determine.

3.And it checks the status of the computer keyboard, RAM, HDD, CD Drive, and other computer hardware's are working correctly.

POST is power on self test is run to check if all the necessary hardware is present and in order

Booting is a process or set of operations that loads and hence starts the operating system, starting from the point when user switches on the power button