Electrical cables and plugs
The following is based upon the British system but the same standards apply very widely across the world.
A cable used to connect a household appliance to the mains has three smaller cables within it. Each is made up of a bundle of fine wires to allow the cable to bend easily without the wires breaking. Coloured plastic covering each individual lead insulates each part of the cable so that the current does not short-circuit within the cable. The colours identify the earth, live and neutral wires. The outer cable covering protects from fraying, rubbing and crushing.
Within the plug the cable clamp prevents the wires becoming loose from the terminals if the cable is jerked. The copper strands of the three wires within the cable should not be visible. If they frayed and became loose then there could be short circuit within the plug. The maximum fuse value is 13 amps but smaller values are used for light load devices.
The first part of the video lesson below covers cables and wiring a plug.