A Code First developer uses a development approach that focuses on defining models and relationships through code before the database is created. They write classes to represent database tables and use attributes to define properties and relationships. These classes are then used by an Object-Relational Mapper (ORM) to automatically generate the database schema. This approach allows developers to have full control over the application logic, promotes rapid development, and makes code easier to manage and version. The developer can also use migrations to handle database changes and updates, ensuring the database and code stay in sync.