Long Path, an earth pony living in Canterlot, and his best friend, a griffon named Free Agent, set out in the company of Twilight Sparkle to visit various places and species to look into what makes them different, and hopefully learn how to get along with them better. Things rarely go to plan though, and along the way, they discover things about themselves, and find love, drama, and laughter. Then Chrysalis changes everything, and the fate of the whole world might be at stake. Their lives will never be the same!
This story is set mostly after the events of Conversations in a Canterlot Cafe and builds on the fanon of the series, especially changelings, so you might want to read those stories first for background material.