A godparent is an adult who sponsors a child during a formal religious ceremony or rite. Many religions have godparents or other adults who do something almost the same. These religions include Christianity & Judaism. Usually a godparent must be a member of the religion of the child.
Originally a godparent was someone who agreed to help raise the child and help them to become a good member of the religion. They may also have taken over as parent to the child if both its real parents died. Today, the role of godparent is not often a formal one, and has no real responsibility to the child. A female child of a godparent is a goddaughter. A male child of a godparent is a godson.