Enter vs Return key?

Sorry if this has already been asked, but I was wondering - what is the difference between the return key and the enter key on my keyboard? For me - I hardly ever use the real "enter" key near the command key. I always use the regular enter key above the shift, but yet it is actually a "return"? I also noticed that holding the FN key while pushing return makes it the "enter" key because it is in the gray font on the key. Any info on the differences of these keys? Thanks!