Database persists state and before it can be queried that sate must be saved. A new Customer entity is instantiated by the Application then sent to Persistance to be saved. When the application needs a certain Customer from the db, the Persistence (usually the Repository) restores the Customer.
Note that the Customer is a Business entity, related but not the same with a Customer table or a Customer ORM entity which is simply a data structure modeled from the database point of view to be optimized for queries.