Representational state transfer (REST) is a style of software architecture. REST is an “architectural style” that basically exploits the existing technology and protocols of the Web.
RESTful is typically used to refer to web services implementing such an architecture.
Google Reader API / Facebook API / Twitter API are good examples of the RESTful service.

He is a technology evangelist, Salesforce trainer, blogger, and working as a Salesforce Technical Lead. After working in Java based project implementation, he jumped to the Salesforce system on a whim and never looked back. He fell in love with Salesforce’s flexibility, scalability, and power. He expanded his knowledge of the platform and became a Certified App Builder, Administrator, Platform Developer I, II, SalesCloud Consultant, total 11 x certified while leading the Salesforce implementation and technology needs. He has worked in a wide variety of applications/services like desktop, web and mobile applications.