The Rotom Pokedex is one of the newest features in the Seventh Generation. In order to make the more efficient Pokedex there has ever been, Kukui developed a Pokedex that Rotom itself could inhabit to create the best possible experience and aid to New trainers. The Rotom Pokedex contains many features that a regular Pokedex doesn't, including a map that shows where you need to go next and advice on such, but still has all the features of a Pokedex. It contains The Alola Region Pokedex.
As you go on your journey, your Rotom Pokedex will be on the bottom Screen of your 3DS at all times, showing you a real-Time view of the map and your movement. This special map also gives you icons on where to go next, just in case you get confused or don't know exactly where you should be heading. However, this feature can easily be changed to the Pokedex simply with a tap of a button.