Dielectric Material in a Capacitor

[reising1]

Can anyone explain the concepts behind dielectric material inside a capacitor. Why is the capacitor able to store more charge exactly? Thanks!

 

[ideasrule]

This diagram may help:

http://en.wikipedia.org/wiki/File:Capacitor_schematic_with_dielectric.svg

The dielectric's molecules are polarized by the electric field produced by the plates, and decrease the electric field between the plates. This means for a given Q, V is reduced (since V=Ed). C=Q/V, so capacitance increases.