How is a conductor different from an insulator?

A conductor allows electrons to move freely from particle to particle whereas an insulator does not.

This is mainly metals as metallic bonding creates a sea of delocalised electrons that can flow freely.

Molten ionic substances also conduct electricity as they have free e - that can move.

Just to clarify, there are different kinds of conductors, mainly heat and electricity.

A conductor is something that is able to allow heat/elect to flow through it easily whereas insulator, basically means the opposite