ORM is a technique that allows you to fetch from and manipulate a database by using an object-oriented programming paradigm. ORM is really good for programmers, because it relies on object-oriented concepts rather than database structure. It also makes development much faster and reduces the amount of source code. ORM is mostly independent of databases, and developers don't have to worry about vendor-specific SQL statements.

JPA provides object-relational mapping for Java developers. The JPA entity is a Java class that presents the structure of a database table. The fields of an entity class present the columns of the database tables.

Hibernate is the most popular Java-based JPA implementation, and is used in Spring Boot as a default. Hibernate is a mature product, and is widely used in large-scale applications.