This song is one of my most favourite songs. It is very meaningful. I have a personal interpretation of this song and would like to share it. I don't know whether the director (Kunal Kohli) intended to pass "this" message to the viewers.
The song comes towards the end of the movie, when the female protagonist Rhea feels that Karan, whom she has known for years is "the one" she will like to spend the life with. The song truly depicts the female perspective on relationships.
Rhea and Karan are walking in rain when they come across 3 different couples. While Karan is a little 'high' after having a drink, Rhea is more congnizant than normal. It seems as if everything she is seeing has a message for her.
When she looks at the old couple, the man playing the piano and the woman enjoying it, she imagines Karan and herself in their place. The question she seems to be answering in her mind is whether their relationship will survive the tests of time or how would it be sharing her entire life with Karan. The first thing that comes to a woman's mind when she enters a relationship is "permanence". She has to be sure that things will work out in the long run.
Next, they meet a married couple. Their car has broken down. The husband is trying to sort out the problem, while the pregnant wife gets some coffee for him. Rhea takes a moment and thinks about having a "family" with Karan. Together, they will be responsible for bringing into the world another life, "their baby".
The third couple they meet are a young dating couple. The guy is putting a ring on girl's finger, a ritual which signifies "commitment". The smile on Rhea's face when she looks at this couple suggests that she is ready to get into this relationship.
A quick jump to the future and a life lived in "reverse gear", is what Rhea experiences in this song.
In the end, after dedicating a post to this song from HUM TUM I would like to accept that I m a romantic fool and a movie buff (what a combo!).
May be i observe things which do not exist.