why is rest api used code example

Example 1: what is a REST API

An endpoint is one end of a communication channel. 
it would be represented as the URL of a server or service.
In REST APIs, the resource typically refers to some object or set of objects 
that are exposed at an API endpoint. 
An endpoint by itself is just 
a reference to a URL that accepts web requests that may or may not be RESTful.

Example 2: which language can be used in restful api

JSON and XML are the two markup language
that can be used in restful web api

for programmin I use java