I agree with Bleedinglove. There is someone that I have extremely strong feelings for, and well, he does for me too. But we live in different states (we have met in person but weren't able to actually date at that moment).
But this song is most definitely about the distance trying to tear you apart, but your feelings for each other being so strong that distance does not matter, and it shouldn't matter ever.
I must say that my biggest dream ever is going the make the distance even bigger, but our hearts will remain together, I will miss him terribly, but it will all be for us to have a better future together.