Confused about butter, don't laugh

Thanks for all the great ideas for breakfast, some mentioned using butter. Is butter one of those "try it and see" things? Although it's an animal product, it's also dairy. I handle chicken, beef ok, but not butter. The food chart I refer to says unsalted butter is ok, but salted butter not. Makes no sense to me. Anyone have any clarification on butter? I just know I react badly to it, waah.