Studying Spring Framework and its projects:
The Java Persistence API (JPA) is a Java programming language application programming interface specification that describes the management of relational data in applications using Java Platform, Standard Edition and Java Platform, Enterprise Edition.
Spring Data JPA is intended to help the creation of a JPA data access layer for you project.
It standardize how build a data access layer but you can still use Hibernate for example to map entities.
Diving Into Dev 