Contrary to the two answers above, electrons moving in a circuit are actually very slow. It is in the range of a few metres per second. The speed at which a change of velocity moves through the circuit is called the signal speed. Depending on the material, it can be a third to a half of speed of light.
Imagine pushing a steel rod. The rod starts to move slowly. As you can see, it moves slowly. Actually, it doesn’t. However, the information you push down on the rod moves at the speed sound – 6000 miles per hour. The rod can only travel a few miles per hour if it is pushing the atoms. However, the push is transferred at high speed from atom toatom.
The same holds true for electrons. The circuit is full of electrons. One electron can be pushed in at one end of a circuit. The fact that there are many electrons means that they travel at the speed of light. An electron from the opposite end is almost immediately ejected. Although it is not the same electron as before, all electrons are identical and one will be just like it.