>>3113696Medium format is a larger format. In film, a bigger negative is produced, and in digital, a larger sensor is used.
In both cases, more light as able to be captured, and that translates to significantly greater detail, shallower depth, micro-contrast, etc... And it's used because it looks killer in the hands of someone competent.
Any wedding photographer worth his salt in the day used a medium format film camera.
But it's a bit of a niche thing as you need to be able to gain access to a real lab to get your stuff developed, but after a while you can truly create amazing stuff.