Official site: Pokémon Sun and Pokémon Moon
Starters (Anyone who doesn't pick Rowlet is wrong):
Article describing some of the new features: Feature: Pokémon Sun and Moon - Breaking Down The Most Exciting New Features
Gyms look like they're getting replaced by Island Trials, a series of small quests eventually leading into a boss battle with a Totem Pokemon, who summons smaller Pokemon to their aid, and then a fight with the island's kahuna.
Hyper Training: For the min-maxers, there's Hyper Training which allows you to increase the actual IVs of your Pokemon, which was not previously possible.
Regional Pokemon: Some Pokemon have changed form due the climate of their region, i.e. Sandshrew and Sandslash become Ice/Steel instead of Ground.
Starters (Anyone who doesn't pick Rowlet is wrong):
Article describing some of the new features: Feature: Pokémon Sun and Moon - Breaking Down The Most Exciting New Features
Gyms look like they're getting replaced by Island Trials, a series of small quests eventually leading into a boss battle with a Totem Pokemon, who summons smaller Pokemon to their aid, and then a fight with the island's kahuna.
Hyper Training: For the min-maxers, there's Hyper Training which allows you to increase the actual IVs of your Pokemon, which was not previously possible.
Regional Pokemon: Some Pokemon have changed form due the climate of their region, i.e. Sandshrew and Sandslash become Ice/Steel instead of Ground.