In Symfony, an entity refers to a PHP class that represents a mapped database table or collection. It is used to interact with the database and encapsulates the business logic and attributes related to a specific domain object. An entity class is typically created under the "src/Entity" directory and is defined using PHP annotations or YAML/XML configuration files in the case of Doctrine ORM. These annotations or configuration files define the mapping between the entity and the database table, specifying fields, relationships, constraints, and other metadata.