Basically a living person is baptized for those that have died giving that person the opportunity to accept the gospel. That's why genealogy is an important process to be completed so that you can have given your entire family history the opportunity to be baptized. My brother a Melchizedek Priest (Elder) has traced our family to its roots and baptized every last one. He is also responsible for the Elders on their missions in San Fernando, Ca so he does a lot of work.