Object Relational Mapping (ORM) is a programming technique to map data from a relational database to Object oriented domain model. This is the core of Hibernate framework.
In case of Java, most of the software is based on OOPS design. But the data stored in Database is based on Relation Database Management System (RDBMS).
ORM helps in data retrieval in an Object Oriented way from an RDBMS. It reduces the effort of developers in writing queries to access and insert data.