Electronics - Capacitors - Discussion

The dielectric constant or relative permittivity of a material under given conditions reflects the extent to which it concentrates electrostatic lines of flux. In technical terms, it is the ratio of the amount of electrical energy stored in a material by an applied voltage, relative to that stored in a vacuum. Likewise, it is also the ratio of the capacitance of a capacitor using that material as a dielectric, compared to a similar capacitor that has a vacuum as its dielectric.

eg:
Air 1
vacuum 1
Paper 4
Rubber 7
Teflon 2.1
Polystyrene 2.5

Bottom line: if you make a capacitor with air as the insulator, and it measures 100 pF, and then change to paper as the dielectric without changing any dimensions, the capacitor is now 400 pF.

What is meant by dielectric constant. Can anyone explain me?

How could we say that it is in between 6 and 8000?