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.
From the MarkScanners Easier to read manual:
Replay Options Your scanner Replay feature acts as an instant replay of the transmissions you’ve just heard. You can set how long a period Replay records for instant playback. This period can range from 30 seconds to 240 seconds (4 minutes). While you can replay any recording immediately and continue replaying it, you cannot save it for future listening.
You can also record transmissions. When you begin recording, your scanner adds the Replay recording buffer to the recording. These recording sessions are saved and can be replayed on demand. Recording has to be started every time you turn on the scanner. Rename and delete sessions through the Review Recordings submenu. You can also copy your recordings from the SD card to your computer in "Mass Storage Mode". Easier to Read BCD436/536HP Digital Scanner Manual