A many-to-many relationship means each record in one model may be related to many records in another model, and vice versa. For example, users may have many roles and each role may belong to many users.

The database uses an intermediate pivot table, such as role_user, containing the two foreign keys and optionally extra pivot attributes. Eloquent defines belongsToMany on both models and offers helpers such as attach, detach, sync, and syncWithoutDetaching to manage the associations safely.