These are the patterns that tell the scanner "I'm a QR Code". They are shown in Off-white and Grey. They come in 3 sub groups: Finder Patterns, Timing Strips, and Alignment Patterns
The Finder Patterns are the most recognizable, the 3 square shapes in the corners. These are used to define the orientation of the qr code relative to the scanner.
The Timing Strips are used to identify the rows and columns during scanning.
The Alignment Patterns appear in Versions 2 and above, and my understanding is they are used to correct for warping, if the paper curls or something. As such, there are more as the Version increases