What is the story behind the song?

I quickly roll the lock of the door and I know quite well the view that awaits me inside. There is a cheesy shoe rack at the entrance, a painting on it, the big-headed, skinny man I drew with oil paints in high school, the living room on the left, Leo rolling in the middle, our kitchen corridor on the right, and my cellar room by the sunlight filtering through the window. I turn my key one last turn and push the door inward. I greet the eternity that surrounds me and the memories I have never experienced, people I don't know flowing all around me, toll booths, escalators, clinking glasses, streets, bells, copiers, skateboards, buzzing cars...