In Jainism, “Baaras” (बारस / બારસ) simply means:

> The 12th tithi (lunar day) of the fortnight – Dvādaśī.

So when people say:

• “Baaras ni puja” – it means doing puja on the 12th tithi.
• “Baaras no upvas / 12 upvas” – fasting on that 12th tithi (usually done regularly through the year).

So, Baaras is not a special separate type of puja, it is mainly the date (tithi) on which you choose to do puja, upvas, or other Jain rituals.

You can read more about the idea of 12 upvas (Baaras upvas) here