Mormons believe that some religious ordinances (like baptism) are necessary for salvation and that if a person isn't baptized while alive then a baptism can be

Mormons believe that some religious ordinances (like baptism) are necessary for salvation and that if a person isn't baptized while alive then a baptism can be performed for them after death. Members of the church are encouraged to research their own family history and perform these ordinances for their deceased ancestors.