> I was curious what it was for so I YouTube'd and searched for instructions on what the soap dispenser was for and (kind-of) to my surprise it was soap to lather and clean your anus with your other free hand. After you lather and clean, you basically rinse your hand with the hose as well.
There seems to be two kinds of cultures in the world: those that use water / their hands for post-business cleansing, and those that use paper or some other medium.