This gets asked often...I should write an instructable on it. Electrons hate each other. They fight. They fight so much that they are constantly trying to get away from each other, and will happily FLOW (current) through conductors which allow them to get from somewhere more negative to somewhere more positive. Think of electric charge like similar-poles of a magnet, they repel one another, but attract to the other side. This difference in electric charge is called voltage. more voltage = electrons want to get to the other side more. Batteries and other electrochemical 'pumps' use a chemical reaction to create a part of a circuit that is more negative on one side than the other. When you put these in a circuit, electrons flow from the negative side, through the conductor to the positive side, and stop. The chemical reaction forces this voltage difference between + and -. How many electrons flow at a given time is called the Amperage. Think of it like a river, a flowrate. It's measured in Coloumbs/second (a coloumb is a number of electrons). Like a pipe where water flow would be gallons per second, or litres per minute, etc. The amount of WORK that can be done by the elecricity is a measure of POWER, which is measured in Watts. It's the volts (how much the electrons want to get from - to +), times the amps: (how many of them there are). Analogy time! Small creek flowing on almost flat terrain: low amps, low volts = low watts. Amazon river flowing on almost flat terrain: HUGE amps, low volts = medium watts Small creek falling off a mountain (like angel falls): small amps, HUGE volts = medium watts Niagara Falls, large river falling off a tall cliff, Huge amps, Huge volts = GIGANTIC watts! Now, components: Conductor: allows electrons to flow from point a to point b. It does this by having spots in the molecules that are willing to accept and/or give up electrons easily. Think of a pipe, or a freeway. Resistor: a not-very-good-conductor. Most every conductor is a resistor to some degree. Measured in ohms, resistance is how much energy is absorbed by the conductor. Capacitor: technically it doesn't conduct internally, but just acts like a battery or storage tank. Simply put, it's 2 disconnected plates next to each other hooked to each side of the circuit. electrons can enter and fill up the plates (lots of surface area = more storage). When you remove the power source, it will stay 'charged' and those electrons can be drained later. Common applications are smoothing out 'bumps' in voltage, since they absorb the extra, and slowly let it back out. Alternately, when theres a dip, they give the electrons back out to make up the difference. Transistor: a switch that is turned on or off by electricity. There are LOTS of varieties, but basically, power flows through them when you apply a voltage to the controlling line. They also act as a one way valve, only allowing power to flow through them in one direction. The 'control' line usually doesn't draw much power. In this way, the transistor can use a small signal to control power to something MUCH bigger than the signal could by itself. This implementation is an AMPLIFIER. Diode: a semiconductor (think "conducts sometimes") that like a transistor only allows power to flow in one direction. Think of it as 'forcing electrons to jump off a cliff', they can hop down, but not up. LED: Light emitting diode. A diode like any other, only allows power to flow one way, but when those electrons jump off the cliff, they land on a light-emitting layer that absorbs some of their energy and spits out light. Lastly: When electricity was discovered (first as static electricity, the buildup of electrons on one side of a disconnected circuit) - it was believed that whatever was flowing (they didnt know was) was the POSITIVE particle. It became common practice to think that power was thus the flow of positive bits thru the circuit. Since then, it was discovered that indeed ELECTRONS flow. The old way of describing positive flow is now called CONVENTIONAL current, but since all the symbols and circuits were drawn using conventional, they stuck.