120, 620 and 220 are all medium-format films–the film width is the same. 220, however, is twice the length of 120, which generally means that 220 yields twice as many exposures. 220 film has no backing paper and usually requires a special film back to shoot. it.620 film is exactly the same as 120 except it's spool is much thinner and more narrow. This was a Kodak invention back in the day. Some cameras take 120, some 620. Being as 620 is no longer manufactured, 120 film can be respooled on 620 spools so those old cameras can keep on living.