The Church has defined the seven sacraments, most clearly in the documents from the Council of Trent in the 16th century. That council was called in response to the Protestant revolt against the authority of the Church. Prior to that period, the most important councils had been called to settle some matter of doctrine. It took a few councils to settle the understanding of the Trinity, that Jesus was fully God and also fully Man, and that there was one God but three Persons. In the 8th century, they had an ecumenical council to address the challenge against pictures of God raised by the Moslems. Some Christians had been influenced by Moslem prohibitions on images of their prophet and thought the Christian church should likewise be cleansed of these images, and they held a council to answer that question with the final answer being “no.”
When we study the sacraments, we generally group them as sacraments of initiation, of healing, and of service. In the early Church, and today in RCIA, one would see baptism, confirmation, and first eucharist in quick succession at the Easter Vigil. These three sacraments constituted the initiation of the unbaptized pagan into the Catholic Church. The two healing sacraments address physical and spiritual healing. And there are two sacraments of service in which one is called to glorify God by a life of self-gift either to the entire Church or to one’s spouse in marriage.