the olive theory

so basically, it referes to the theory from how i met your mother which says that the potential of a relationship is determined by whether one person in the relationship loves olives while the other one don't. In this case, the one who hates olives gave them to the other so they completed eachother. But the theory is not just about opposing points fitting well together : the most important thing is about willing to sacrifice something you love, to give it to the other.

Ted Mosby, HIMYM : The olive theory is based on my friends Marshall and Lily : he hates olive, she loves them. In a weird way, that's what makes them such a great couple.

Later, Marshall actually admitted that he liked olives but gave them to Lily because she loves olives more