Why living beings like / dislike things in the world?

All living beings (animals + humans) like something, and they don't like some another things? What is the reason for liking and disliking. Eg: Imagine there are two best friends let's call friend A and friend B. Friend A likes a lady call X (very pretty lady) meanwhile friend B doesn't like lady X. What's the reason according to the buddhism. To narrow down the question the point is though lady X is very pretty for friend A but not for friend B. Why is it?