"Real cute" is improper English, but it is used so often that I think most English speakers don't realize it. "Cute" is an adjective, so to modify it in English, you need an adverb and not another adjective as an adjective can only modify a noun. "Really" is the adverb form of "Real." So "Really cute" is proper English. "Real cute" is not proper, but it is commonly used to mean the exact same thing as "Really cute."
So when you read where someone has written it, the meaning behind what they wrote is exactly the same. However; "Really cute" is proper English. Knowing which is proper is very helpful in many situations. :)