The regions consists mainly of four islands plus the Aether Paradise
The Northwestern island the player starts out on and simplest in layout. It consists of a path leading to the Ruins of Conflict through Iki Town and a single loop going from Route 1 to Hau'oli City, Route 2 and Route 3, each with a couple offshoots, namely Ten Carat Hill on Route 1 by the Professor's House, Melemele Meadow and Kala'e Bay on Route 3. There is a single Trial on this island, the Normal Trial led by Ilima in Verdant Cavern. The Grand Trial has the player fight Hala. Tapu Koko is the guardian deity of Melemele Island, found at the Ruins of Conflict
Akala is the Northeastern island in Alola and the second island the player travels to. It is the most content dense island with 3 Trials; the Water trial in Brooklet Hill led by Lana, the Fire trial in Wela Volcano Park led by Kiawe, and the Grass trial in Lush Jungle, led by Mallow as well as the Grand Trial where the player fights Olivia at the Ruins of Life. The island's layout is complex and goes over itself with the initial port being Heahea City that leads the player onto Route 4 to Paniola Town to Route 5's western end at Brooklet Hill. As the player goes south on Route 5, they head East through Royal Avenue into Route 7 and 8. At Route 8's end the player reaches Route 5's Northern end and Lush Jungle. From there, the player has to go south back to Heahea City to get to Diglett's Tunnel to get to Konikoni City and Akala Outskirts. Going east from Heahea City leds to Hano Beach. Tapu Lele is the guardian deity of Akala Island, found at the Ruins of Life
Ula'ula is the Southeastern island in Alola and the third island the player travels to. It is home to 2 trials; the Electric trial on Mount Hokulani, led by Sophocles and the Ghost trial in the abandoned Thrifty Megamart led by Acerola as well as a Grand Trial against Nanu. It is also the home to the Pokémon League, upon the summit of Mount Lanakila. The island's layout is summed up as branching paths. The port starts the player in Malie City where they have to go through Route 10 to get up Mount Hokulani. After returning to Malie City, the player can take the other path through Route 11 into Route 12 (which has some optional offshoots). After arriving in Tapu Village, the player has to go to the Aether House on Route 15 before they can go to the Thrifty Megamart in Route 14. The player then has to go through Route 16, Ula'Ula Meadow and Route 17 to make it to Po Town, a haven for Team Skull. Tapu Bulu is the guardian deity of Ula'ula Island, found at the Ruins of Abundance.
Poni Island is the Southwestern island in Alola and the least inhabited. It is home to a single trial, the Dragon trial as well as a Grand Trial against Hapu. Poni's layout is a lot more wild with lots of open space and winding paths. The player starts on the only real settlement on the island; Seafolk Village. There is a villager that offers rides to Exeggutor Island. From Seafolk Village, the players goes into the Poni WIlds and then the crossroads at the Ancient Poni Path. Going down along Poni Breaker Coast will lead to the Ruins of Hope. Going north through Vast Poni Canyon leads to the Altar of the Sunne / Moone. In the post-game, going through Poni Grove will lead to the wide area of the Poni Plains which splits into a path leading to Resolution Cave and a path leading to the Battle Tree. Tapu Fini is the guardian deity of Poni Island, found at the Ruins of Hope.
Aether Paradise is a Very Large Floating Structure that serves as an artificial island inbetween all the islands. The island has a jamming signal that makes empty Poke Balls ineffective. It contains four floors.
Alola lacks a normal Pokémon league and gyms. Instead, trainers have to complete Island trials (which involve completing a Trial Captain's challenge and then beating a Totem Pokémon) and beating each island's Kahuna. Prior to Sun and Moon, the completion of all 7 trials and the 4 Grand trials led to a final festival where the Island Challenger would face the 4 kahunas again in a row but, by the end of Sun and Moon, this has been formalized into a Pokémon League with an Elite Four
A total of 81 new Pokémon were introduced in Alola and 19 alternate forms to existing Pokémon. In Alola, there are in total 300 native in the region with 28 available through Island Scan.