In the Church, an ordinance is a sacred, formal act performed by the authority of the priesthood. Some ordinances are essential to our exaltation. These ordinances are called saving ordinances. They include baptism, confirmation, ordination to the Melchizedek Priesthood (for men), the temple endowment, and the marriage sealing. With each of these ordinances, we enter into solemn covenants with the Lord.
Other ordinances, such as naming and blessing children, consecrating oil, and administering to the sick and afflicted, are also performed by priesthood authority. While they are not essential to our salvation, they are important for our comfort, guidance, and encouragement.
Ordinances and covenants help us remember who we are. They remind us of our duty to God. The Lord has provided them to help us come unto Him and receive eternal life. When we honor them, He strengthens us spiritually.