Question

How does a voltmeter give its reading? The process.

Answer 1

A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit.
How it gives reading and the working process :
(i) Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit.
(ii) Digital voltmeters give a numerical display of voltage by use of an analog to digital converter.

To understand the exact process of Voltmeter, you should have college-level knowledge about how various semiconductor devices work and what are its properties. Its a very advanced topic by which only you can understand the exact process of VTVM-s and FET VM's.
Most VTVMs and FET-VMs handle DC voltage, AC voltage, and resistance measurements; modern FET-VMs add current measurements and often other functions as well. A specialized form of the VTVM or FET-VM is the AC voltmeter. These instruments are optimized for measuring AC voltage. They have much wider bandwidth and better sensitivity than a typical multifunction device.
However, I appreciate you passion for showing interest in knowing the working process.