There are 4 new islands. 1 in which is large.
OmaOmao Island
Anuenue Island
Pikachu Island
Safari Island

~Green/Leaf makes an appearance.
~Yellow makes her debut for the first time in the games.
~Gold, Silver, and Crystal make an appearance.
~ Cyrus makes an appearance and talks about studying worm holes for the future.
~ Giovanni makes an appearance.
~ Darkrai can now be caught in game.

~ There are 22 new Alolan Forms:
Oddish, Gloom, Vileplume and Bellossom.
Togepi, Togetic, and Togekiss
Growlithe and Arcanine
Slugma and Magcargo
Phanpy and Donphan
Hoothoot and Noctowl
Cherubi and Cherrim
Octillery
Jumpluff
Stantler
Mantine
Forretress

~ There is 14 new Mega Evolutions:
Mega Empoleon Sun
Mega Empoleon Moon
Mega Torterra
Mega Infernape
Mega Meganium Sun
Mega Meganium Moon
Mega Typhlosion
Mega Feraligatr
Mega Moltres
Mega Articuno
Mega Zapdos
Mega Braviary
Mega Krookodile
Mega Zoroark

~ There are 4 new Primal Reversions:
Primal Ho-oH
Primal Lugia
Primal Cresselia
Primal Darkrai

~ There are 2 new Battle Bond Transformations:
Serena-Delphox
Clemont-Chesnaught