The first heaven is ALL that we can see, including the stars, moon and anything else that is visable from earth in 'outer' space'. It is the PHYSICAL of the universe. The 2nd heaven is a SPIRITUAL realm in which the demonic reside. The 3rd heaven, also a spiritual realmed location, is the location of the Throne room of God and where Jesus is seated at His right hand. It is the realm/location from wihich He commissions His angels to do His bidding. We know that in the book of Daniel, Michael the Arc Angel informs Daniel that he was detained from bringing answer to his (Daniel's) prayer because in coming from that place of being commissioned by God to answer that prayer, the 3rd heaven, he encountered and had to fight the prince of Persia which is a spiritual metaphor for a territorial demonic principality. Since the demonic cannot enter the 3rd heaven, it is understood that in order to get from the 3rd heaven to us, they must pass through the demonic-infested 2nd heaven.
Maggie