Do you want to define it or explain it? You define it by saying current is the net movement of charge. You explain it by saying that current in a wire moves by the drift of electrons, as I explained earlier using the marbles-in-a-hose analogy. The drift method is not a deep heavy concept that will derail anybody.
Same thing about 'the speed of electricity'. I want a simple way to explain electricity with out making a one hour talk about things that the questioner does not want to hear.
Electricity is a generic word. What aspect of electricity do you want to explain about? If you are referring to speed, the charge carriers travel at a slow drift speed in a wire, but the response moves at the speed of light.
Capacitors (and inductors) are not like resistors. A 'perfect' cap does not heat.
Yes, that is well known.
Ratch