The bottle contains a potent concentrate of bug-killing juice. The user is meant to squeeze the base of the bottle, causing a measured amount of product to be drawn up into the heart-shaped chamber, which is graduated. In order for the drawing action to work, air needs to come in from somewhere, and the other cap on the tower-like portion of the bottle serves as a valve. That side of the bottle is shaped like a handle while the other side curves like a spout, hopefully making it obvious that you're meant to pour one way but not the other.
And yes, I recognize that since I worked as a structural package designer (fancy-talk for bottle designer), I may be the only one geeking out over this thing.