This essentially means we're being told or one tells us. It is conversational present tense. In English you might say "We love cheese and we're told the best comes from France." Or in French "Nous aimons le fromage et dit-on le meilleure vient de la France."

Aye correct comment dit on means "how do you say" or "how do they say" (lit) "how is it said" Pourquoi dit-on..... why do we say

I've also heard one of my French friends say 'comment dit-on', I think it translates to 'How do you say?', as a trendy phrase to use. Like: (Comment) dit-on très cool!

maybe they say "dis donc!" It litterally means "say, so" but it's just a way to get someone's attention. Like Ex: "Dis, donc ! T'as vu lu le nouveau film au cinéma ?" I found a page explaining this http://french.about.com/od/vocabulary/a/dis-donc.htm