Why is there grysol in meats?

It seems like in a lot of meats I eat, there seems to be at least one grysol. I'm not so sure if I'm spelling it right but I really want to know why it is in there. I know in chicken, it's apparently still eatable but it is really chewy and I can't eating that. I don't like th real hard grysol either that sometimes I find in beef. What exactly does it do and why is it in all of these meats? Also, are there ways to get meat without it?