Dave KC has it right. Every manufacturer makes their own proprietary air suspension (unless one specs a Hendrickson). Freightliner calls theirs Airliner, and Peterbilt calls it Air-Trac (stiffer with torsion bars under the springs) or Low-Air LEAF for straight trucks. I went with the Low-air leaf on my 335, and it is almost too soft. The box wiggles left to right as I travel- kind of annoying.
Point: the terms are synonmous...