If the sibling comment isn't enough detail, see https://en.wikipedia.org/wiki/SuperGun

"Supergun" is a term for an adapter intended to allow JAMMA-compatible arcade boards to be used with standard home video equipment. Normally, you'd need an arcade cabinet with a JAMMA port, compatible arcade-RGB display, and all the wiring harnesses behind it, but that is a space hog and most people don't want one in their house.