Logical explaination of this code

Hi guys, i need a short explaination of this code :

  Vector2?[] oldTouchPositions = {
					null,
					null
			};

what Vector2?[] is? i mean the ?[]

Explanation is here

http://stackoverflow.com/questions/16773891/what-does-the-operator-mean-in-c-sharp-after-a-type-declaration

It states that the variable is Nullable.