Whey Protein Vs. Creatine?

I've been going to the gym for many months now and i've started to develop a lot of muscle especially in my upper body, although... it doesn't show quite as much as i would have liked. so people suggested that i use either creatine or whey protein. which one does what? people say whey is all around the best for your body for development, and others say that creatine will make your muscles show up even more (that is if you already have some)? so i guess this is obvious that i should choose creatine but i'm not sure which one to use because i don't really know what they do. (keep in mind i've already built up quite a lot of muscle in both upper and lower body, although primary focus is on upper body e.g pecs, shoulders, and arms.) (oh and ps. i'm a guy, so yeah i want to look quite muscular, people say that im big but when i tense i just looks big it doesn't really look muscular and toned :(