Mailstream Plus - What is the USPS definition of the term IMb Post Net Barcode?

Product Feature: Parameters

The IMb barcode definition according to the USPS:

The Intelligent Mail barcode combines the data of the existing POSTNET™ and the PLANET Code® barcodes, as well as other data, into a single barcode. The Intelligent Mail barcode is a type of height-modulated bar code, that uses four distinct vertical bar types (Full, Tracker, Ascender and Descender)
UPDATED:  October 26, 2017