I believe they are refering to the headers that are associated with recordings created by the x36 scanners.
These scanners, when the recording function is turned on, will create files (in WAV format) and store them on the SD card for the scanner. These files, recordings of received transmissions, can then be transferred from the scanner to a computer.
The programs discussed elsewhere allow folks to look at the "header" data for each recording file. That data will have information including channel name/tag, system name/tag, department name/tag, etc.