“Campaign” is a confusing word in AL. As a D&D player, you may think of your home game or group as running a “campaign”. And that’s true. But AL uses the word “campaign” to also mean “setting” (I said it was confusing).
AL currently has 5 campaigns:
When you create your character, you must decide which of the above campaigns your character will belong to. A character can never change campaigns. For example, if you create a Forgotten Realms character, you cannot change them to be in the Ravenloft campaign.
<aside> 💡
Unless you have a specific reason to choose a different campaign, create your character in the Forgotten Realms campaign.
</aside>
Most adventures also belong to certain campaigns. For example, Tyranny of Dragons is part of the Forgotten Realms campaign. Most (if not all) DDAL adventures are also part of the Forgotten Realms campaign. Whereas Dragonlance: Shadow of the Dragon Queen is part of the Dragonlance campaign. A character can only play adventures that are available to that campaign.
However, some adventures can be played by characters from more than one of the above campaign. For example, Curse of Strahd can be played by both Forgotten Realms and Ravenloft characters.
You can often determine the campaign that an adventure is part of based on the adventure’s code. Please see Adventure Codes for a list of codes and their campaigns.
<aside> 💡
Unless an adventure (or AL Adaptation Guide) says otherwise, assume the adventure is part of the Forgotten Realms AL campaign.
</aside>