Among all the number of different Islands found in Sea of Thieves, five of them are known as Outposts. When you first begin the game, you will randomly be placed at one of the five different Outposts. Believe it or not, you actually can only encounter the three different Trading Companies at Outposts, meaning you can undertake Voyages by first visiting an Outpost. On top of this, all of the Merchant Shops can only be found on islands designated as an Outpost.
All Known Outposts In Sea of Thieves
Ancient Spire Outpost
Dagger Tooth Outpost
Galleon's Grave Outpost
Plunder Outpost
Sanctuary Outpost