Here's why:

* Conductors: Wires are made of conductive materials like copper or aluminum. These materials allow electrons (the carriers of electricity) to flow freely through them.

* Insulators: Insulators are materials that resist the flow of electricity. They have tightly bound electrons that don't move easily. Examples include rubber, plastic, and glass.

* Protection: The insulator acts as a barrier around the wire, preventing the electricity from flowing out to anything that touches it. This is crucial for safety, as it stops electric shocks and fires.

Think of it like a garden hose. The water (electricity) flows through the hose (wire), and the hose's outer layer (insulator) keeps the water from spilling out.