Here is just a little intro to it. Ohm's law shows the relationship of voltage and current in an ideal conductor. The relationship states that:

The potential difference (the voltage) across an ideal conductor is proportional to the current through it.

The constant of proportionality is called the "resistance", R. Or the opposition to the flow of electrons through a material.

Ohm's Law is given by:
V = I R or I=V/R or R=V/I

where V is the potential difference between two points which include a resistance R. I is the current flowing through the resistance.