Need help on ps4 edition of minecraft

They very recently rolled out the update 1.9 something or other. Which added things like slow cookers, blast furnaces and cartography table. I'm having s hard time understanding how exactly the "new" mapping system works and how the cartography tables work. (Every time I expand a map it expands to an area I havent even explored yet) can some please (in simple terms) how this all works?