The D&D Adventurers League is an ongoing official campaign and organized play for Dungeons & Dragons. It uses the fifth edition Dungeons & Dragons rules, and features the Forgotten Realms setting. You can play D&D Adventurers League games literally anywhere. Players use the fifth edition rules to create a character and bring that character to games anywhere D&D Adventurers League play is happening.
More information and important documentation can be found on the official D&D Adventurers League website.