What is the difference between a ribeye steak and a rib steak?

a rib eye is the same as prime rib at a restaurant. Except that a steak is cut from the roast ahead of time rather than the whole roast cooked then cut off before you serve it. Rib eye is "marbled" tender juice and very flavorful. a rib steak is a generic term for any piece of beef that is harvested from the rib area of the animal. Many cuts of beef are from this area. However many times they are all marbled well and flavor full. Sometimes they are not as tender though.

Rib-eye is very flavorful but you'll have to trim a lot of fat and also it can handle being cooked to higher levels of doneness without being too dry. ( although better medium to medium-well but won't be a hockey-puck at well-done). Sirloin is much leaner therefore dries out quickly, so if you insist on ordering your steak well-done(which is not a good choice) sirloin is not the cut to order. America's Test kitchen and Alton Brown do a wonderful job of explaining the various cuts of beef in more technical detail.