pH meter is Standardised by pH 7 & calibrated with pH 4 & 9.2. i searched about that but i haven't found much difference. then Why these two diffrent terms
You would have noticed that one is acidic and other is basic pH. It is just to confirm that at both ends of the pH scale the pH meter is working fine.
As far as I know the whole process is known as calibration by three pH tablet solutions for checking the acidic basic and neutral ph of the meter reading