It is very important Pooja as it is performed for the peace of the departed paternal and maternal souls. Shradh is performed only by the predecessor can accomplish peace and freedom.
In different Hindu Puranas like Agni Purana, Garuda Purana and Mastya Purana the importance and criticality of Shradh is mentioned and specially in Garuda Purana it is clearly mentioned that those souls which do not get pind daan, tarpan meander erratically on the Earth and it is the duty of predecessor to do pind daan to satisfy the soul.
Shradh is the ritual which is performed to satisfy the dis-satisfied wishes of the predecessor’s souls which are caught in our reality because of powerful urges that stays within the soul even after the death.
When Shradh Pooja is done then it purifies every wrong and helps them rest in peace with their souls freed to look for their favours.
Shradh Puja is performed in Pitru Paksha period amid the Krishna Paksha fortnight in the Ashwin month.
One of the best example of why shradh puja should be done can be seen in Mahabharta in which when Karna dies his spirit goes to paradise and there his soul is offered only Gold and Silver because he donated Gold and Silver ornaments to poor but never gave food to anyone or to his forefathers and after that Karna told to Indra that he was not aware about his ancestors and hence never offered anything to them. Then Indra gave him 15 more days to go back to earth and perform shradh Pooja in the name of his predecessors.
Each year shradh Pooja is performed for 16 days and each day or tithi is dedicated for an ancestor. In the light of the tithi, petitions are offered for the peace and freedom of the departed soul.
The first day of shradh is Amavasya and on this day supplies are offered so that the departed souls rest in peace and also to find its place in heaven. Shradh puja is performed by the male member of the family and of possible the eldest male member should perform the shradh ceremony.
It is also believed that if shradh pooja is performed with full belief and dedication then the departed soul rests in peace and also blesses their kin with assurance, peace, and happiness.