Pitru Paksha - Mahalaya Paksha

Shrardha is nothing but, that ritual which is done with Shradha.

Brahma Puran says during the Krishna Paksha of Ashwin maas lord “Yamraj” grants freedom to souls so that they can accept the offerings made by their children on earth.

A 16days lunar is dedicated every year for the pitrukarmas and are termed as
Pitru Pakshya, Pitri Pokkho, Solah Shraddha, Kanagat, Jitiya, Mahalaya Paksha and Apara Paksha.

Chautha Bharani and Bharani Panchami, the 4th and 5th Tithi - for people deceased in the past year.
Avidhava Navami - 9th Tithi, is for married women who died before their husband
The 12th Dwadasi is for children and ascetics.

The 13th of Trayodashi, a ritual of Kakabali is performed for the dead children
The 14th tithi is known as Ghata chaturdashi and is reserved for those people killed by arms, murders, wars

Every human should perform 5 yagnyas during the journey of life
Deva Yagna (worship of Devas)
Pitru Yagna (worship of one's forefathers)
Bhuta Yagna (worship of other beings)
Manushya Yagna (worship of fellow humans)
Bramha Yagna (worship of knowledge)

Bhramadevas sons Pitru-ganas and their respective Pitru Devtas rule our last 3 generations in the ascending order (pitaha - Father, pitamah - Grandfather and Pratipitamah - Great Grand Father)

NARAYANA in his moolarupa, took the forms for various events of shrishti, sthiti & laya. These anntaryami swarupas rule each of the last 3 generations & help the souls attain their moksha & these souls have capacity to see their in-dwelling god as per their sadhna & capacities

The linked spiritual dwellings

ANNTARYAMI -> PITRU DEVTAS -> PITRU GANA -> PITRUS

1. Kritipati Pradyumna -> Vasu -> Kavyavaha ->Agnishvatas -> Pitaha
2. Jayapati Sankarshana-> Rudra->Yamah ->Barhishad -> Pitamah
3. Mayapati Vasudev -> Aditya -> Soma -> Somapa -> Pratipitamah

The Pitru ganas come and take the shrardha offerings done during the 16days period. They stay in urdhvaloka or Somaloka. They come onto earth in Manomaya kaya (Kama Rupa - The body of Desire ) & get into the body of the Bhraamanas we invite for feeding.

These ganas come in form of Vaayu Rupa and accept the bhojan offered to the them. Along with people who know the time and dates of deceseased,

Pitru Paksha also be performed by people who don't remember their parent's Tithis, Those who couldn't do the shradha in the year due to various reasons.They can choose a prescribed day by the purohits as per the deceased tithi. Pitru paksha is major kriya for Karma saaphalyata

Pitru devtas gain the offerings from their lineage performing shrardha in some or the other form as per their janma. Pitru Dosha nivaran is blessed during the pitru paksha and they bestow you with deergha aayu, sakala vidhya, akhanda dhana and putra pautra and prapautras.

All humans give anajali or tarpan with water to their ancestors three times. All the fingers should be joined and water is offered watching the aditya (Sun).
On mahalaya amavasya Tila tarpana is done by all including grihastas to their deceased ones.

Only on mahalaya Amavasya people can perform tila jala tarpana. Pitru Runa needs to be actively
taken care of and seek their blessngs during these auspicious days of Bhadrapad and Ashwin.

People who don’t do the Shradh for their Pitru Devtas suffer from “Pitru Dosh” as their Pitras got angry and return back being neglected.

माता च पार्वती देवी पिता देवो महेश्वरः ।
बान्धवाः शिवभक्ताश्च स्वदेशो भुवनत्रयम् ॥