REST resources are the fundamental elements of any RESTful web service. A REST resource can be defined as an object that is of a specific type with the associated data and is optionally associated with other resources. It also exposes a set of standard operations corresponding to the HTTP method types, such as the HEAD, GET, POST, PUT, and DELETE methods, using the @HttpMethod annotation.
Resource classes are Java POJO classes, which use JAX-RS annotations to implement a web service. Each resource class must have at least one method annotated with @Path or a request method designator (@HttpMethod). Only public methods of a resource class can be exposed as resource methods.