IIRC heaven is like hell in that there are different levels. It's something like
Level 3: God
Level 2: Angels
Level 1: Humans & whatever (pet goldfish?)
No, its all the same place, there's just a hierarchy. Its something like:
God, Seraphims, Cherubims, Thrones, Dominions, Virtues, Powers, Principalities, Archangels, Angels.
I found some references to the third heaven,
this seems to sum it up pretty well. If you're too lazy too read that, here's a simple, short explanation:
The third heaven: A Jewish expression for that heaven which was beyond (1) the air, and (2) beyond the sun and stars; the secret place of the Almighty.
They mostly reference 2 Corinthians 12:2.