Pairin and nukta: the last nine shapes of Gurmukhi
After the 35 core letters and the vowel signs, nine shapes remain: three subjoined pairin letters that tuck under a consonant to blend it, and six nukta letters, ordinary letters wearing a dot that shifts their sound. They are the last stop before you can read anything Punjabi throws at you, including the first line of the Mool Mantar.
The three pairin letters
Pairin means "at the feet": a small rara, haha, or vava written under a consonant blends into it. ਪ੍ਰ reads "pra". The buried haha is the subtle one, since it often surfaces as tone rather than an audible h, which is why ਪੜ੍ਹ (read) does not sound like "parh" spoken by an English reader.
A small copy of Rara tucked under another letter. The two sounds blend into one quick cluster, so ਪ + ੍ਰ reads 'pr'.
A small Haha hiding under a letter. It adds a light breath that in everyday speech usually turns into a tone, as in ਪੜ੍ਹ.
A rare little Vava under a letter, adding a quick w glide. You will mostly meet it in careful or classical spellings like ਸ੍ਵਰ.
The six nukta letters
The dot (nukta) under these letters marks sounds that entered Punjabi through Persian, Arabic, and English loanwords: z, f, x, and friends. In relaxed speech many speakers fold them back into the base letter, saying "jaroor" for ਜ਼ਰੂਰ, so treat the dotted sounds as the careful form and you will understand both.
Sassa (ਸ) with a dot below becomes 'sh'.
Khakha (ਖ) with a dot below: a raspy 'kh' from the throat.
Gagga (ਗ) with a dot below: a soft throaty 'gh'.
Jajja (ਜ) with a dot below becomes 'z'.
Phappha (ਫ) with a dot below becomes a true 'f'.
Lalla (ਲ) with a dot below: a retroflex 'l'. Regional; recognition only.
Do you need them on day one?
No. The core 35 letters and vowel signs carry you through most beginner text, and that is the order the app teaches. But names, song lyrics, and newspapers use pairin and nukta constantly, so they are worth a focused week once the core letters feel solid.
Keep going: the full alphabet chart · the vowel signs · Gurmukhi vs Shahmukhi
Learn the whole script in the app. The Gurmukhi track goes from zero to reading, with tracing on every letter, and every lesson is free.