The two terms are are so similar they are commonly mistaken for each other (admittedly, that has happened to me too!) and so I have it all nutted out here for you.
A rib eye is more commonly known as a scotch fillet in Australia, however the two are almost the same. As the term suggests, this cut of meat is derived from the rib of a cattle. The term 'rib eye' is more commonly used when the meat is still attached to the rib bone. Where the rib bone has been removed, the term 'scotch fillet' would be more commonly used to describe this cut of meat. The meat from this area of a cattle is usually well marbled with a large and noticeable line of fat through it. Because of the fattiness of this cut of meat, it is very flavoursome.
An eye fillet is also known as a beef tenderloin in Australia, and is found beneath the rib next to the backbone of a cattle. Because this muscle does not do a lot of work, its texture is butter soft and very tender. However it is also a very lean cut of meat that lacks fat and connective tissues, and so it is often suggested that it is not cooked beyond medium rare (50% pink centre). Cooking beyond medium rare will cause the steak to be dry and chewy - ew!