The fundamental unit of electricity is 'charge'. Each electron is slightly negatively charged and it is this movement of charge around a circuit which powers our appliances. The speed of the electrons/the number of electrons which are flowing per second is known as the 'current'.To get these electrons moving, we need to apply a "pushing force". This is done by supplying a 'potential difference' a.k.a. a 'voltage'. If we increase the voltage, each electron has more energy; this means our circuit can run more power-hungry components. Equally, the greater the "pushing force" (voltage), the faster the flow (current).Each component within a circuit will have a certain amount of 'resistance'. This is like a "blocking force" and reduces the flow of electrons (current).