If space is something and it is expanding what is it expanding into

the question rests on the premise that it is expanding :O

This is our problem, we have a mental-block with the idea of empty-space expanding into a void, into which there currently isn't any space, although there is nuuuuthing there! And what IS "space" anyway? It's dark, because there's nothing in it. It's intensely cold, because there's no heat there, and it's a better vaccuum than we can make in any laboratory on Earth. Essentially, "Space" is nothingness itself, but we try to envisage it as a tide of SOMETHING spreading into a void. Well, what the hell is the VOID?
It makes our little Human heads spin. You may as well be a dog, asking "How did that bird fly away from me, when I chased it? Woof!"

Think of when the Michelson-Morley experiment thought that a medium was required for light to travel through, you are making an assumption based on Newtonian mechanics and not allowing for seemingly impossible occurrences to occur because of it. If you let go of the traditional and mostly wrong system by which we view our universe it should become more clear to you.

It is expanding into an unknown element called x.3oyel.Researchers conclude space is an imaginary substance floating into this element.Will keep updated with this info shortly.

They don't know yet and believe me don't bother yourself about it,it's a matter of god and no one can tell you about it because till now they can't see farther than 90% of expected space

Is space expanding or is the UNIVERSE expanding?

A massive cloud of tiny Baby Jesus particles, glittering in the blackness of oblivion.

Ah, my young padawan, THAT is the real mystery of the universe!

Oprah's pants.