According to Hindu mythology, the souls of three preceding generations of one's ancestor reside in Pitru–loka, a realm between heaven and earth. This realm is governed by Yama, the god of death, who takes the soul of a dying man from earth to Pitru–loka. When a person of the next generation dies, the first generation shifts to heaven and unites with God, so Shraddha offerings are not given. Thus, only the three generations in Pitru–loka are given Shraddha rites, in which Yama plays a significant role.According to the sacred Hindu epics (Itihasa), at the beginning of Pitru Paksha, the sun enters the zodiac sign of Virgo (Kanya). Coinciding with this moment, it is believed that the spirits leave Pitru–loka and reside in their descendants' homes for a month until the sun enters the next zodiac—Scorpio (Vrichchhika)—and there is a full moon. Hindus are expected to propitiate the ancestors in the first half, during the dark fortnight.
When the legendary donor Karna died in the epic Mahabharata war, his soul transcended to heaven, where he was offered gold and jewels as food. However, Karna needed real food to eat and asked Indra, the lord of heaven, the reason for serving gold as food. Indra told Karna that he had donated gold all his life, but had never donated food to his ancestors in Shraddha. Karna said that since he was unaware of his ancestors, he never donated anything in their memory. To make amends, Karna was permitted to return to earth for a 16–day period, so that he could perform Shraddha and donate food and water in their memory. This period is now known as Pitru Paksha. In some legends, Yama replaces Indra.
The fifteen days of Malaya Paksha consists of 15 Tithi (also called Thithi). They are Pratipat, Dvitiya, Tritiya, Chaturthi, Panchami, Shashti, Saptami, Ashtami, Navami, Dasami, Ekadasi, Dvadasi, Trayodasi, Chaturdashi, Amavasya (new moon). According to Hindu mythology, every individual's who wants to perform this Pitru Tharpanam, they should do it on the same day of their ancestor died which will fall within any one of these fifteen days.
The performance of Shraddha by a son during Pitru Paksha is regarded as a compulsory by Hindus, to ensure that the soul of the ancestor goes to heaven. In this context, the scripture Garuda Purana says, "there is no salvation for a man without a son".The scriptures preach that a householder should propitiate ancestors (Pitris), along with the gods (devas), ghosts (bhutas) and guests.The scripture Markandeya Purana says that if the ancestors are content with the shraddhas, they will bestow health, wealth, knowledge and longevity, and ultimately heaven and salvation (moksha) upon the performer.
The performance of Sarvapitri amavasya rites can also compensate a forgotten or neglected annual shraddha ceremony, which should ideally coincide with the death anniversary of the deceased. According to Sharma, the ceremony is central to the concept of lineages. Shraddha involves oblations to three preceding generations—by reciting their names—as well as to the mythical lineage ancestor (gotra). A person thus gets to know the names of six generations (three preceding generation, his own and two succeeding generations—his sons and grandsons) in his life, reaffirming lineage ties.Anthropologist Usha Menon of Drexel University presents a similar idea—that Pitru Paksha emphasises the fact that the ancestors and the current generation and their next unborn generation are connected by blood ties. The current generation repays their debt to the ancestors in the Pitru Paksha. This debt is considered of utmost importance along with a person's debt to his gurus and his parents.
The shraddha is performed on the specific lunar day during the Pitru Paksha, when the ancestor—usually a parent or paternal grandparent—died. There are exceptions to the lunar day rule; special days are allotted for people who died in a particular manner or had a certain status in life. Chautha Bharani and Bharani Panchami, the fourth and fifth lunar day respectively, are allocated for people deceased in the past year. Avidhava navami ("Unwidowed ninth"), the ninth lunar day, is for married women who died before their husband. Widowers invite Brahmin women as guests for their wife's shraddha. The twelfth lunar day is for children and ascetics who had renounced the worldly pleasures. The fourteenth day is known as Ghata chaturdashi or Ghayala chaturdashi, and is reserved for those people killed by arms, in war or suffered a violent death.
Sarvapitri amavasya ("all fathers' new moon day") is intended for all ancestors, irrespective of the lunar day they died. It is the most important day of the Pitru Paksha. Those who have forgotten to perform shraddha can do so on this day. A shraddha ritual performed on this day is considered as fruitful as one conducted in the holy city of Gaya, which is seen as a special place to perform the rite, and hosts a fair during the Pitru Paksha period.In Bengal, Mahalaya (Bengali: মহালয়া) marks the beginning of Durga Puja festivities. Mahalaya is the day when the goddess Durga is believed to have descended to Earth. Bengali people traditionally wake up early in the morning on Mahalaya to recite hymns from the Devi Mahatmyam (Chandi) scripture. Offerings to the ancestors are made in homes and at puja mandaps (temporary shrines).MatamahaDauhitra ("Daughter's son") also marks the first day of the month of Ashwin and beginning of the bright fortnight. It is assigned for the grandson of the deceased maternal grandfather.The ritual is also held on the death anniversary of the ancestor. The shraddha is performed only at noon, usually on the bank of a river or lake or at one's own house.Families may also make a pilgrimage to places like Varanasi and Gaya to perform Shraddha. ("Mother's father") or
It is essential that Shraddha is performed by the son—usually the eldest—or male relative of the paternal branch of the family, limited to the preceding three generations. However, on Sarvapitri amavasya or matamaha, the daughter's son can offer Shraddha for the maternal side of his family if a male heir is absent in his mother's family. Some castes only perform the shraddha for one generation.Prior to performing the rite, the male should have experienced a sacred thread ceremony. Since the ceremony is considered inauspicious due to its association with death, the royal family of Kutch, the king or heirs of the throne are prohibited from conducting Shraddha.
The food offerings made to the ancestors are usually cooked in silver or copper vessels and typically placed on a banana leaf or cups made of dried leaves. The food must include Kheer (a type of sweet rice and milk) , lapsi (a sweet porridge made of wheat grains), rice, dal (lentils), the vegetable of spring bean (guar) and a yellow gourd (pumpkin).
The male who performs the shraddha should be take a purifying bath beforehand and is expected to wear a dhoti. He wears a ring of darbha grass. Then the ancestors are invoked to reside in the ring. The shraddha is usually performed bare-chested, as the position of the sacred thread worn by him needs to be changed multiple times during the ceremony. The shraddha involves pinda-daan, which is an offering to the ancestors of pindas (cooked rice and barley flour balls mixed with ghee and black sesame seeds), accompanying the release of water from the hand. It is followed by the worship of Vishnu in form of the darbha grass, a gold image or Shaligram stone and Yama. The food offering is then made, cooked especially for the ceremony on the roof. The offering is considered to be accepted if a crow arrives and devours the food; the bird is believed to be a messenger from Yama or the spirit of the ancestors.A cow and a dog are also fed, and Brahmin priests are also offered food. Once the ancestors (crow) and Brahmins have eaten, the family members can begin lunch. 
