Hiya Multicom,
When aircraft were first being built, when you moved the control column it pulled a cable attached to the control surface (eg. aileron, elevator), which made it move and allowed you, as the pilot, to control the aeroplane.
Later, as aeroplanes flew faster, physically moving these control surfaces became harder because of the increased forces on them from the faster moving air around them. So, we engineer types designed them with pneumatic/hydraulic controls to do all the work, to move the surfaces for you. These were still actuated by the pilot's control column.
But now, modern technology has advanced to the point where computers can monitor almost every aspect of the aircraft for you.... and these electronics were encorporated into the systems that moved the control surfaces. So, when the pilot makes a control input in the cockpit, eg. moves the control column forwards, this is identified by the associated cockpit technology as an electrical signal, and will be sent as electrical inputs to the hydraulics and/or motors. They then move the elevator down the amount that the electrical inputs tell them to.
Also, the cockpit technology recieves feedback from the hydraulics and/or motors as to how much force is needed to move the control surface. As an example of why that's useful, the electrical information is translated through motors attached to the control column enabling the pilot to 'feel' what the aeroplane is doing. It all just allows for much easier, safer (and yet more detailed) control and management of the aeroplane you are flying.
Replacing cables with wires has coined the phrase 'Fly-by-Wire'.
It's late so that might have come out not only garbled but inconcise.. but I hope it helps you :-)
Andy.