In Dungeons & Dragons, a character class is kind of like being in a special club. Each club has its own special powers and abilities that you can use to help you on your adventures.
For example, if you choose to be a fighter, you are really good at fighting with weapons like swords and shields. But if you choose to be a wizard, you are really good at using magic spells to help you out.
There are lots of different character classes to choose from, each with their own strengths and weaknesses. Some are good at sneaking around and being stealthy, while others are good at healing their friends when they get hurt.
When you create your character, you get to pick which class you want to be part of, and that will determine what kind of abilities and powers you will have. As you play the game and your character gets stronger, you can learn new abilities and become even more powerful in your chosen class.