As a reminder, QR (Quick Response) codes are made up of a web URL (e.g. www.example.com), so that when any standard camera phone scans a QR code the user will be immediately directed to a landing page on the web. We use the web URL https://tgz.bz because shorter URL's mean higher fidelity when printing QR codes onto packaging.
In the Polytag world, a static QR code contains only the GTIN (13-digit barcode number) of the product. An example of this is https://tgz.bz/01/05000129295481
The "01/" before the GTIN is a GS1 application identifier - this tells any software that a GTIN will follow the 01, and meets global GS1 standards.
A Polytag serialised QR code contains the GTIN plus a 'unique-every-time' 12-digit code.
An example of this is https://tgz.bz/01/05000129295481/21/NzczNTEyZTk4
The "21/" before the 'unique-every-time' 12-digit code is another GS1 application identifier, which tells any software that a serialised code will follow the 21. This means that each QR code on every one of your products is unique.