You ask about transparencies. A transparency is a photo you hold up to the light, so light from behind allows you to view it. You see it as a positive. That is, in all the correct colors. This is different to a negative. When you hold it up to the light, the colors are "reversed" and it's difficult to understand what the photo will look like when made into a positive. Most transparencies are 35mm slides. That is, they are small transparencies (3.5cm or 35mm wide). A 35mm transparency is usually mounted in a white cardboard holder. Larger transparencies can measure up to a giant 15cm or 150mm wide, and these are usually not mounted in cardboard. You also can't take large-format transparencies with an ordinary 35mm camera. Color magazines prefer transparencies and usually slides will do. A transparency is a "positive" and there is no intermediary "negative". On the other hand, color print film is developed and is a negative (the colors seem reversed), and from this negative a positive, or print, is made. Hope this is clear enough.