Genetic load: can someone explain?

Can you explain this so even I can understand it?

Thank you. I understand all the words now and the different cases makes sense.I would guess that the independent or synergistic effect cases are the more common?I think I could now tie this back to the OP but I'm going out (and would rather someone else (who might get it right) did it first. (Later I will try).Then I'll have to review the information to see the evidence for the synergistic case in humans.

From the OP: So this basic assumption must be met. If they are synergistic then deleterious mutations do not pile up and become such a problem. That is the average fitness does not drop to as low as 0.05.Right?However, I know realize that I don't know how "average fitness" is determined or what it means. It seems to suggest that if it is 0.5 then half of offspring survive to reproduce. That makes some kind of sense.Now then how do we decide if it is actually synergistic?It makes sense to me that it might be. Obviously, there will be cases where having one moderately deleterious mutation might not be enough to stop reproduction but a second one is fatal? Correct?