[DallasMike]

I'm not very bright, so can someone here explain in simple layman's terms exactly what the universe is expanding in to.

That's a very bright question. The answer is that the universe isn't expanding into anything. There is nothing but God outside the universe. Not even space or time.

[Surtur]

Thank you for your reply. I can accept that God is outside the universe just as He is inside for His essence permeates the whole of creation.