Miss Cruz's class has a battery, wires, a bulb and a switch on every desk.

Donna joins her parts into one loop, and she presses the switch.

The bulb lights.

Donna's parts, joined into one loop. The bulb is lit.

A circuit is a complete loop from one end of the battery, through the bulb, back to the other end.

This is the same circuit drawn two ways.

One circuit, drawn two ways. Left, as a picture. Right, as a diagram.

Miss Cruz asks, 'Four kinds of part, and the bulb lights. What job does each part do?'

Donna's circuit as a diagram, with each part named: the battery, the wire, the bulb and the switch.