Exploration works very literally: at the start of the game, Characters – as well as usually their Players – do not know much about what lies beyond the horizon. At the end of an introductory arc, they will be given strong reasons to leave wherever they are and start exploring.
Then, during a long campaign of travels – in active play as well as in downtimes – the Players will collect information about the world: physical maps as well as written hooks and secrets about the world. They subsequently can use these to shape their route through the world according to their own agendas.