What is the Law of Conservation of Charge?

The conservation of charge simply states that can neither be created nor destroyed.

In other words, if an object (or part of an object) gains charge, another object (or part of an object) must lose charge.

For example, if you rub a comb through your hair, it will become negatively charged. The only way for this to happen is for your hair to also become positively charged. So if the comb's charge becomes -1 mC, the charge in your hair must become +1 mC.