( The 'th' in this name is pronounced like 'th' in 'with' . Ri is the vowel sound like in Krishna. The last is for plural number.)
The word 'pithri' literally means father, but it refers to all one's anacestors. According to our mythology, the dead mortals will reach the abode meant for such souls, if they have had virtuous deeds to their credit. All such manes absorb with the seven deities there, named 'Pithris'. The names of these deities are Kavyavaaha, anala, Soama, Yama, Aryama, Agnishvaaththa and Barhishada.
It is for the purpose of securing a place for parents and themselves as well in this abode that people observe penances and practice several austere procedures.