Spring Data JPA implements the core functionality defined in Spring Data Common interfaces.
JpaRepository is the JPA-specific repository interface:
public interface JpaRepository<T, ID extends Serializable> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
SimpleJpaRepository is the default implementation of the CrudRepository interface for JPA:
public class SimpleJpaRepository<T, ID extends Serializable> implements JpaRepository<T, ID>, JpaSpecificationExecutor<T>
