To know the difference, you have to be in such relationships. They may not necessarily have to be two different relationships; your relationship could simply transition from immaturity to maturity. In fact, that is the basic difference between the two; time.
A mature relationship takes time to develop; it doesn’t even come close to love-at-first-sight or anything of the sort. It’s not something that keeps you up at nights, if anything; it helps you sleep more peacefully. Your life may treat you with a pile of problems, but a mature relationship wouldn’t add to them, rather help you through them.
Here are a few things that set apart a mature relationship from an immature one;