You’ll be going from 1 to 10 in Exile’s Reach, and once you finish that, you’ll be sent to Kul Tiras or Zandalar to take part in Battle for Azeroth’s story which is the most direct setup for Shadowlands. Now, if you’re a brand new player or starting a new character on a new account, the decision is made for you. There are a lot of options - The Burning Crusade, Wrath of the Lich King, the post Cataclysm world of Azeroth, Cataclysm’s at the time endgame, Mists of Pandaria, Warlords of Draenor, Legion, and finally Battle for Azeroth‘s current content will become a leveling zone as well.
One of the choices you’re going to have leveling through World of Warcraft‘s next expansion, Shadowlands, is deciding which of the game’s expansions to go 10 to 50 in.