Remember we said before that the three basic parts for most of the electricity that we see every day are:
Voltage, current, and resistance.
We can learn about electricity by comparing it to how water flows through a pipe.
We learned that voltage is like the speed that the water is going.
and that current is like the size of the pipe.
You can think of the Resistance as anything in the pipe that would slow down the water.
So if the pipe got smaller in the middle, that would make it so not as much water could flow through.
(from: wikipedia - hydraulic analogy)