In Jainism, “Punam” (Poonam / Purnima) means the full‑moon day. It is spiritually important, not just a calendar date.

1. General importance of Punam in Jainism

• Punam is counted among the special “5 tithi” (Chauth, Ashtami, Chaudas, Amavasya, Purnima).
• On these tithis, doing tap (fasting), swadhyay (study), pratikraman, jaap, puja gives much more punya compared to normal days.
• Many Jains try to at least do:

- Upvaas / Ayambil or some niyam - Visit derasar, listen to pravachan - Reduce violence, control food and speech ( jainknowledge.com)

2. Special Poonams in the Jain year

(a) Chaitri Poonam (Chaitra Purnima)

• Very important day on Shatrunjay (Palitana).
• On this day, many great munis attained moksha on Shatrunjay, including Pundarik Swami (first Gandhar of Bhagwān Rishabhdev) and crores of monks.
• Connected with Navpadji Ayambil Oli (its last day).
• Doing yatra, tap and bhakti on this day is believed to give very high spiritual benefit. ( jainknowledge.com)

You can read more here

(b) Kartik Poonam (Kartik Purnima)

• On this day, after four months of Chaturmas, the Shatrunjay Giriraj yatra restarts.
• Many tirths that were “closed” for yatra during chaturmas reopen.
• People again start eating green leafy vegetables which were avoided in chaturmas.
• Traditionally, it is also connected with many souls getting moksha from Shatrunjay on this day. ( jainknowledge.com)

You can read more here

3. Simple way to honour Punam

Even if you cannot do big yatra, on any Punam you can try:

• At least one extra prarthana or Navkar jaap
• Some tap: upvaas, ekasanu, beasanu, or no‑raag/dwesh niyam
• Swadhyay: read or listen to Jain granth for some time
• Daya & daan: avoid hurting even the smallest beings more carefully; give small charity with right bhav

So, Punam in Jainism is a special day for stronger sadhana and faster karmic purification, and some specific Poonams like Chaitri Poonam and Kartik Poonam are extremely important due to their connection with Shatrunjay and many siddha–bhavya souls.