Arca Swiss developed a mounting system that uses a plate on the camera and a respective clamp on a tripod head or bracket.
You can find a pdf of the AS classic system
here.Many different manufacturers make so called AS 'compatible' plates and brackets, though they don't all fit each other. So calling a plate an AS plate is lot like calling a box of tissue a box of Kleenex. It's become the standard term with no standard for exactly what quality and dimensions the AS plate/clamp may be.
Many fit each other, most are good quality, but they're not all the same. Fun huh ?
I think most would agree that the actual AS brand and
Really Right Stuff are the best. Though you still have quality products from
Markins and
Kirk.
So you have to pick a brand and jump in. A good way to decide on which to use is by deciding what tripod head/clamp you want to use.
(OK Ellis, your turn)