Answer:
Relative means that it is compared to something. For example, the relative charge of a proton is +1 and it is relative to that proton. The relative charge of an electron is -1 relative to protons. That means it is exactly the same, but opposite. The relative charge of an up quark is +2/3, and that means that the charge of that quark is 2/3 of the charge of the proton. It depends what it is compared to.