Marine Vinyl and standard vinyl are really the same thing, except marine-grade vinyl has two extra features. It has additional UV protection to prevent the color from fading in sunlight. And it also has antibacterial and antifungal additives to make it mildew resistant.
Marine vinyl is great for any outdoor application or anywhere else it would be exposed to direct sunlight or moisture. Uses include outdoor seating, awnings, and boat cushions, but you can also use it indoors.
Marine-grade does not necessarily mean higher quality than standard vinyl, just that it’s UV and mildew resistant.