Try googling, reference and non-reference video card. From there you would be enlightened. Summary would be like,
Reference video cards, would be cards made by amd, then companies would just like put a sticker or something on it and would sell them, and what would matter would be warranties and the likes.
Non-reference video cards, usually these are those that you would see with dual fan or more. The companies would use the same gpu and sometimes change the board and stuffs to improve performance and would also put their own fan/cooling solution on it to improve cooling.