Postal Kit (residence-permit yellow envelope)
Plain English
It's the yellow envelope you pick up for free at certain post offices when you want to apply for or renew your permesso di soggiorno. Inside you'll find the two forms (Modulo 1 and Modulo 2), the instructions, and the payment slips. You fill it in at home, then bring it back to the counter with your documents.
Why it matters
This is the only way to file a residence-permit application in Italy. You can't do it online, you can't email it, and you can't walk it into the Questura. The day you hand the kit over the counter is the official start date of your application, so the receipt matters.
Real example
"Liu grabbed the yellow envelope at his local post office in Padova on a Tuesday, spent the evening filling in the forms with help from a patronato, and was back at the counter Thursday morning to submit it with his fee payment."
Common confusion
Not every post office does this. You have to go to a branch with a "Sportello Amico" service, and you'll pay an extra postal handling fee on top of the actual permit fee.
Official source
Poste Italiane (Sportello Amico)