"Think of water flowing through a pipe, an insulator is like a pipe that's frozen: electrons can't get through. Semiconductors are materials that change from free-flowing conductor to a frozen insulator and back again, simply by zapping them with an electric current."
A very good link this is....
Feel free to be the first
Please review the linked page for context.
If you can think of something better than this,
please add it to the database