First of all, new Pokemon. I'm going to speed through this part because these aren't the crazy new features that I'm talking about. But one of the new Pokemon is called "the synthetic Pokemon" and is a normal type named "Type: Null", colon and everything. This new Pokemon has set the Pokemon community ablaze with theories on what exactly this creature is, but if you want more info, the Pokemon website is an excellent resource. They've got several paragraphs for each and every new Pokemon announced so far.
Next is Pokemon Sun and Moon's day and night cycle. The first of some cool new mechanics for this upcoming game. Pokemon Sun and Moon are set 12 hours apart. Pokemon Moon owners will have their current time plus 12 hours as their time in-game. Additionally, the games will feature different Pokemon encountered in the wild, (the example given in the Japanese trailer was Pokemon Sun's Drifloon to Pokemon Moon's Misdreavus) different Totem Pokemon, (example given was Pokemon Sun's Gumshoos to Pokemon Moon's Alolan Raticate) and of course Pokemon Sun's Solgaleo to Pokemon Moon's Lunala.
After that was the grand reveal of Pokemon Sun and Moon's good guys: the Aether Foundation. The Aether Foundation is said to "care for Pokemon that have been hurt". The island found in the middle of the Alolan Region that had been previously theorized to be home to the Pokemon League, is actually home to the Aether Foundation. There they care for Pokemon while also conducting various research projects. The leader of the Aether Foundation is called Lusamine, and is describe as the foundation's "glamorous president". Alongside her are the AF's "branch chief" Faba and "assistant branch chief" Wicke. Working for the foundation are Aether Foundation grunts, which has led some to believe that the Aether Foundation is secretly an evil team operating under a disguise. But you can be the judge of that until the game comes out.
Next, we are introduced to another member of Team Skull: Gladion, the Team Skull Enforcer. He is shown battling with the new Pokemon, Type: Null, the brutally strong Pokemon. What's interesting is why he was not announced at the same time as all the other Team Skull members, but this probably means nothing.
What really excites me is this next part of the trailer, the return of Dexio and Sina from Pokemon X and Y to help you find the Zygarde Cells. In the trailer, they are depicted giving you the Zygarde Cube which then allow you to find and collect the Zygarde Cells on your journey. Collecting them will allow you to acquire Zygarde's different forms.
It's been called the return of Pokemon Snap: PokeFinder is a tool in your Rotom Pokedex that allows you to take pictures of Pokemon in the wild and inside cities in the Alola region. These can then be shared (on Miiverse maybe?) and receive likes and comments from other trainers.
Last is Pokemon Sun and Moon's biggest mystery and biggest announcement: Ultra Beasts. Ultra Beasts are non-Pokemon creatures that are apparently threatening the Alola region. The Aether Foundation is conducting research on these dangerous beasts, and there are rumors that more than one exist. What is most peculiar about the only announced beast: UB-01 is that it bares a remarkable resemblance to a previously announced human character, who is also surrounded in mystery.
To see this all for yourself, I've included both the American and Japanese trailers because the Japanese one shows more gameplay, which is important at the end when we get a better look of UB-01:
