“In Bhagavad-gita (9.25) it is said, pitrn yanti pitr-vratah. Those who are interested in family welfare are called pitr-vratah. There is a planet called Pitrloka, and the predominating deity of that planet is called Aryama. He is somewhat of a demigod, and by satisfying him one can help ghostly family members develop a gross body. Those who are very sinful and attached to their family, house, village or country do not receive a gross body made of material elements but remain in a subtle body, composed of mind, ego and intelligence. Those who live in such subtle bodies are called ghosts. This ghostly position is very painful because a ghost has intelligence, mind and ego and wants to enjoy material life, but because he doesn’t have a gross material body, he can only create disturbances for want of material satisfaction. It is the duty of family members, especially the son, to offer oblations to the demigod Aryama or to Lord Vishnu. From time immemorial in India the son of a dead man goes to Gaya and, at a Vishnu temple there, offers oblations for the benefit of his ghostly father. It is not that everyone’s father becomes a ghost, but the oblations of pinda are offered to the lotus feet of Lord Vishnu so that if a family member happens to become a ghost, he will be favored with a gross body. However, if one is habituated to taking the Prasada of Lord Vishnu, there is no chance of his becoming a ghost or anything lower than a human being. In Vedic civilization, there is a performance called sraddha by which food is offered with faith and devotion. If one offers oblations with faith and devotion–either to the lotus feet of Lord Vishnu or to His representative in Pitrloka, Aryama–one’s forefathers will attain material bodies to enjoy whatever material enjoyment is due them. In other words, they do not have to become ghosts.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), ” Srimad Bhagavatam”, Fourth Canto, Chapter 18 – Text 18