What is virtual ground in an op-amp inverter?

[uzair_ha91]

What is the principle of virtual ground? Please elaborate.
Attempt:
The input impedance of an op-amp is so high that virtually all input current is shunted to the feedback resistor when is works as interver. When noninverting input is grounded and internal resistance of op-amp is very high, then due to no potential drop the inverting input is also grounded and this is called virtual ground.

 

[Redbelly98]

In these feedback circuits, the op-amp adjusts the output voltage in such a way as to keep the inverting input (-) at or close to ground potential.

However, current cannot actually flow into (-) to ground. That's why it's referred to as a virtual ground.

 

[chroot]

The op-amp attempts to force its inputs to the same voltage. If one input is grounded (i.e. held at 0V), the op-amp will force the other input to also be grounded. It's virtual because you cannot source or sink current from it; the op-amp inputs have very high impedance.

The "virtual ground" principle is really just a special case of the "virtual short" principle.

- Warren