A covenant is a sacred agreement between God and a person or group of people. God sets specific conditions, and He promises to bless us as we obey those conditions. When we choose not to keep covenants, we cannot receive the blessings, and in some instances we suffer a penalty as a consequence of our disobedience.
All the saving ordinances of the priesthood are accompanied by covenants. For example, we make a covenant when we are baptized, and we renew that covenant each time we partake of the sacrament (see Mosiah 18:8–10; D&C 20:37, 77, 79). Those who have received the Melchizedek Priesthood have entered into the oath and covenant of the priesthood (see D&C 84:33–44). The temple endowment and the sealing (marriage) ordinance also include sacred covenants.
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.