It's called Medium Format film, but there are a number of actual crop sizes that fall under that banner. The previous batch was from a 6x6 (cm) square format. The other popular crop size is quite a bit smaller, but still falls under the name Medium Format, 6x4.5 cm. You can see its the more familliar landscape wide-format that we're used to.
It's really all about the resolution obtainable when we put the image on a bigger piece of film. See this example at wikipedia for a size difference.
Here's the first batch from a beautiful camera, the Mamiya 645 PRO.
The decreased Depth Of Field is the obvious part, but there is just something about this format.
This first batch is with a Twin Lens Reflex Mamiya C330 It was inherited from Tali's grandfather who was quite the landscape photographer. These are the results from the first few batches.