REST API concepts and examples

REST API

Application
Programming
Interface

REpresentational
State
Transfer

Chances are whatever website you want to work with has some kind of API that you can use in order to consume their data.

Check out:
http://www.programmableweb.com/category/all/apis

You can consume data from APIs.

You can also write data to APIs.
Http Request Methods:
GET
POST

Postman - REST Client

OAuth