What is the birthright?

Esau acknowledged that Jacob had received his birthright but listed it as separate from his blessing that Jacob also received. That makes me wonder what the birthright was. Is it possible that the birthright Esau sold to Jacob was priesthood authority?

Also, if Jacob and Esau we’re born when Isaac was 60 and Isaac lived to 180 then Jacob would be 120 when Isaac died which must certainly have been after Jacob was married. I think there is some mistake in the record on the timing of some of these things.