Dungeons & Dragons is a game where you pretend to be a character in a made-up world full of magic, monsters and adventure. A campaign is a story that you and your friends make up and play together in this world.
A campaign setting is the world that you will be playing in. Just like how you can make up any story you want, you can make up any world you want too! Some campaign settings are based on real places and times like medieval Europe or ancient Egypt, while others are completely made up.
A campaign setting usually has a map that shows all the different places you can go, like towns and cities, forests, mountains, and dungeons where you can fight monsters. Each place is full of different people and creatures that you can interact with.
The people and creatures in the setting that you meet can give you quests and ask you to do things for them. For example, a king might ask you to go slay a dragon that is terrorizing his kingdom. Or a witch might need you to gather some rare herbs for a potion. Completing these quests will earn you rewards like gold, magic items, and experience points that help you become stronger and better at the game.
When you play Dungeons & Dragons, you get to use your imagination and make up your character's story as you go along. A campaign setting helps guide you on your adventure and gives you a place to explore and build your character's story.