Medium format film and cameras
First of all, medium format cameras use what is called "roll-film". Unlike 35mm film or the new APS film, rollfilm has no outside metal or plastic cannister. It is commonly available in 2 formats called 120 and 220. The only significance being that 220 is twice as long as 120 and so you can put 2x as many pictures on it. They are both wound on plastic spindles with paper to protect the film when putting the film into the camera and taking it out.
120 film is about 6.5cm high by 100cm long. It has a paper backing which extends all the way along the film.
220 film is about 6.5cm high by 200cm long. It only has a paper leader and tail which are taped to the beginning and end of the film. This allows twice as much film to fit in the same space as on a 120 roll of film.

Loading a medium format camera Something that throws 35mm camera users for a loop when the first use a medium format camera is that you never will rewind a medium format film.
It sort of works like this: Imagine an empty toilet paper roll on it's holder. If you were to take the new roll and attach the end of a new roll of paper to it, you'd have one full roll of paper in your hand, and one empty one on the wall. (With me so far?) If you then started rolling the upper (empty) roll and winding the paper from the lower roll onto it, well... That's how medium format film loads, in a nutshell. Once the roll is totally wound onto the one on the top, you take it off, and replace it with the now empty tube/spindle, and start again. I guess that all in all it's sort of the opposite of toilet paper. :)

What sort of cameras can you get in medium format? Just about everything you can in 35mm. There are