Shradh is an important ritual as per the Hindu tradition. It is performed as a Puja to salvation aka atma shanti of departed ancestors (paternal as well as maternal). It is an act of tribute and respect, devotion towards ancestors.
Performing this puja for ancestors will bring good fortune to their descendants and thereby receiving positive energies for progress. The descendant also receives blessings from the pitra/forefathers to help him materially. This can greatly help the individual to progress spiritually as the material obstacles or problems are eradicated. This puja is very powerful and effects on health and curing serious diseases. This is being done for getting recovery from chronic diseases and other body aliments. Those who are invariably suffering from any aliments shall get this puja done for early recovery. This puja is specifically suitable for Success in Business or Career , Protection from Evils and Enemies.
The posture of hand while offering Tarpana varies for offerings made to devas (Gods, Goddesses and Navagrahas), rishis (sages) and pitrus (departed ancestors).
(a) For devas, the offering is made to flow over the four fingers of the right hand other than the thumb.It is believed that one’s pitrus will be eagerly awaiting for tarpana on all the above-mentioned occasions. If no offering is made, they will return to their places disappointed, and the descendant misses their blessings which he would have received, if he had performed his filial duties.