Before we start, it would be a good idea to clarify what electricity is. Electricity can be seen as a stream of electrons. Electrons are tiny particles with a negative charge. So, roughly explained, electricity is a stream of electrons flowing from one point to another.

A good way to explain an electric current passing through a cable would be to imagine a pipe filled with marbles that exactly fit the pipe. If we push a marble into the pipe in one end, the motion would be distributed, each marble pushing its neighbor, so that almost instantly a marble in the other end would be pushed out of the pipe.