JPA vs Hibernate vs Spring Data JPA.

1. JPA (Java Persistence API)

• A Specification (Interface). It defines the standard for ORM (Object-Relational Mapping). It is just a set of rules and annotations (@Entity, @Table, etc.).

2. Hibernate

• An Implementation (Provider) of JPA. It actually contains the logic to map objects to the database. It has more features than standard JPA (like HQL).

3. Spring Data JPA

• A Wrapper / Layer on top of JPA providers (Hibernate). It provides the Repository abstraction (JpaRepository, CrudRepository), allowing you to perform DB operations without writing boilerplate DAO code.