Conductors and insulators are two types of materials that are both very important in things that use electricity. If you look at an electrical cord, you'll see its plastic covering, and two or three metal prongs sticking out of the plug at the end. The plastic is an insulator, which protects you from the current in the cord, and the metal is a conductor, which carries the electricity.
How Electricity Works
All matter is made of atoms, and those atoms have tiny particles called electrons. When electrons move from atom to atom, their movement creates an electric current. Some materials are made of atoms with electrons that can move easily, so they can carry electricity without difficulty. Other materials are made of atoms that don't want to give up their electrons, and can't carry an electrical current.
Materials that like to share their electrons are called conductors. Some examples of good conductors are metals such as copper, silver, and gold. Copper is the most common metal used in electronics, both because it is a good conductor and because it is much less expensive than gold or silver. The insides of most electrical cords, like the ones you plug into your wall, are made of copper.
Insulators are materials that don't share their electrons very easily, so they don't carry electricity. Some examples of good insulators are glass, wood, plastic and rubber. Insulators, like the plastic on the outside of an electrical cord, protect you from being shocked by the electrical current carried by the metal conductor inside the cord. They also separate the different conductors in electrical appliances, so they can't touch at the wrong points, creating short circuits.
Electricity and Safety
If you are doing experiments with electricity, it's very important to only use batteries ---never use the electricity from a plug or wall socket. The current in a wall socket is very high, and is dangerous to humans. Like metal, liquids like water or sweat can be good electrical conductors, so you should never touch anything electric with wet hands. Knowing which materials are insulators and conductors can help keep you safe from electric shocks.