"The Coriolis effect is like being on a merry-go-round. Imagine that you are on one side and your friend is directly across from you on the other. If you were to throw a ball to your friend while the merry-go-round was not spinning, it would go straight to them. This is our one-cell circulation pattern on a non-rotating Earth."

This page has a very good description, with an analogy that explains this phenomenon.