Chapter-1|Electric Charges and Fields | NCERT 12th Physics:
Conductors: The substance through which electric charges can flow easily are called conductors. They contain a large number of free electrons which make them good conductor of electricity.
Examples: Metals, Human, Animals bodies e.t.c.
Insulators: The substance through which electric charges cannot flow easily are called insulators. In the atom of such substances, electrons of the outer shell tightly bound to the nucleus.
Example: Glass, Rubber, Plastic e.t.c.