What is supposed to be given in the aqeeqah of a baby boy or a baby girl? Is it the same if not given on the 7th day of birth?

My sister gave birth to a baby boy last year in March. We couldn't perform his Aqeeqah due to his illness. [This](https://islam.stackexchange.com/questions/1874/what-is-the-right-age-for-circumcision/1890#1890) answer says that the Aqeeqah has to be given on the 7th day. *Questions:* - What is supposed to be given in the Aqeeqah of a baby boy or a baby girl? - What should be given in the Aqeeqah if we couldn't do it on the 7th day?