We always called the difference between Above- and Below-the-line peeps on a crew as the have and the have-nots.
Basically the Above-the-line folks are the creatives: writer, producer, director, actors.
Below-the-line are all the other folks plus all the ‘stuff’, like equipment, locations, offices, post-production items, you name it.
The term Above- and Below-the-line comes form the top sheet of a budget where the summary delineates between the Above and the Below people. In commercial production the two groups are also subject to different mark-ups.