Out of the ten poruthams prescribed by South Indian Astrological rules this comes second is called as "Gana Porutham".
Hindu Rashi/ Nakshatra Matching
In South India, Nakshatra Matching is done to check the Jathagam Porutham of the bride and groom. It is mostly done when the marriages are arranged by the families of the boy and the girl.
The meaning of Gana Porutham in Hindu Marriage Matching / Compatibility
One of the poruthams that are checked for horoscope matching for marriage, is gana porutham. Ganas are three in total; these are Deva, Manusha, Rakshasa. The 27 stars or the asterisms belong to one or the other of the ganas.
Gana chart for porutham
Deva Gana Manusha Gana Rakshasa Gana Aswini Bharani Krithigai Mrigasirsham Rohini Aayilyam Punarpoosam Thiruvadhirai Magham Poosam Pooram Chithirai Hastham Uthiram Visakam Swathi Pooradam Kettai Anusham Uthiradam Moolam Thiruvonam Uthirattadhi Sadhayam Revathi Poorattadhi Avittam
Good gana porutham
It is ideal if the gana of boy and girl in the horoscope are of the deva gana and manushya gana respectively; the gana porutham matching is good.
Medium gana porutham
If both the horoscopes belong to the rakshasa gana, the porutham is medium.
Gana porutham not matching
An example of this is, if both stars are in the rakshasa gana and the boy's star is less than 13 when counted from the girl's star, gana porutham is not matching.
When there is a gana mismatch, there could be mis-understandings in marriage. But if other poruthams match, this of the 10 poruthams for marriage matching may be discounted by some.