Industrial Sewing Machine
A single-purpose machine built for speed and continuous production use, as opposed to the general-purpose domestic machine most home sewists learn on.
Where a domestic machine is a generalist — one machine handling straight stitch, zigzag, and buttonholes at a modest speed — an industrial machine is usually built to do exactly one job, extremely fast, for hours at a stretch. A straight-stitch industrial machine only sews a straight stitch; there's no zigzag, no built-in stitch selection dial. What you get in exchange is a motor and mechanism built for genuinely high speed and heavier fabric without straining, which is why garment factories run rows of them rather than domestic machines.
They're mounted into a table with the motor beneath, run by a knee lift or a foot pedal that's far more sensitive than a domestic machine's — the speed range from "barely moving" to "full speed" happens over a much smaller pedal movement, and it takes real practice not to send the first few test seams flying. I wouldn't recommend one as a first machine for exactly that reason, plus the total lack of built-in stitches; they're a tool for once you already know what you need and why.
Where I do think they're worth the investment: sewing heavy fabric consistently — canvas, multiple layers of denim, upholstery-weight material — that will bog down or skip stitches on a domestic machine no matter how well-maintained it is. That's a limitation of the domestic motor and feed mechanism, not of technique.