Spring Boot is a framework powered by Java. As such, it allows you to use Java code to connect with and interact with a database. Because Java is all about OOP (Object Oriented Programing) the name of the game is to write Java Classes that can be mapped to tables in a relational (SQL) database. The classes are not what technically are mapped, but rather, the objects that the classes generate or instantiate.
In technical terms, We’re talking about an ORM (Object Relational Mapper). This is provided by a Spring Project known as Spring Data JPA.