Bio-Battery battery consists of two different metals suspended in an acidic solution. All batteries have 2 sides, Positive "+" and Negative "-" sides which are called terminals. Electrons flow, like water in a river, from the "-" electrode terminal, let's call it the top of a waterfall, of a battery, through a conductor, towards the "+" electrode terminal, let's call this the bottom of the waterfall, of a battery. When electrons flow from the top of the waterfall to the bottom it is called current. It is very similar to the movement of a real river current but is so small you can't see it.The movement of the waterfall has a moving force that pushes, this movement is called current. When this moving force (current) is measured, it is measured it what is called voltage or volts. This moving force is going to make the LED light up.