You probably already did the essay, but I'll still answer it.
A toaster is just coiled up wires. The wires are connected to electricity that forms a circuit. The wires have a lot of resistance, so the electricity does not flow easily. A wire with resistance in it has a lot of stuff in it so the electrons have a tough time to just move forward in the wire. The electrons bump around with each. There are trillions of them moving around. This generates a lot of heat that comes out of the wires. The heat makes toast. The temperature of the toaster is set by the wire resistance. There is a timer that makes your toast pop up. If you want darker toast the timer just runs longer.
A more difficult question is explaining why the electrons move in the first place just because you plug it in the wall. I don't think anyone really understands it fully, but electrons like to move away from each other, so if you give them a chance to spread out they will do it. This need to move away causes a circuit to flow as they flow to the part of the battery or electric source (plug in your wall) that has less electrons. They call this negative (more electrons) and positive (less electron) terminals. Electricity flows from negative to positive to make a circuit. When they bump into things, like impurities in the wire, it creates heat and even light when a lightbulb is connected.
