In order to make the most efficient Pokedex there has ever been, Kukui developed a Pokedex that Rotom itself could inhabit to create the best possible experience and aid 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 it still has all the features of a regular Pokedex. It contains the entire 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.
As you journey through The Alola Region this time around, the Rotom Pokedex will be much more interactive. After certain intervals of time with no interaction, it will begin to look sad. By clicking on it during this state, the Rotom Poekdex will cheer up and once again becoming engaging. The more fond it grows of you, the more it will communicate, even going so far as to one day call you its Master. By having a great amount of interaction with it, you will also earn the chance at playing its newest feature called Roto Loto. With it, you will be rewarded certain Rotom Powers to further assist you on your journey.