REST stands for "Representational State Transfer". REST is the architectural pattern of the world wide web. In order to focus on the roles of components, REST ignores the details of component implementation and protocol syntax. The constraint upon their interaction with other components and their interpretation of significant data elements.

REST have architecture properties:

1) Performance: Interaction between component is a dominant factor to improve efficiency.
2) Scalability: Support large number of components and interaction between them.
3) Simplicity: Simple interface to understand.
4) Modifiability: One can easily modify the data.
5) Visibility: User can communicate between components.
6) Portability: Data can be moved to some other component.
7) Reliability: Resistant to system failure.

REST also have architecture constraints:

1) Client–server: Separate interface for client and server.
2) Stateless: Web service should not keep a client state on server.
3) Catchable: Data can be cached and used wherever it is required.
4) Layered system: Service should be layered to ensure security policy.
5) Code on demand: It is an optional constraint. It allows clients to improve its flexibility.
6) Uniform interface: Uniform interface define the interface between client and server.

For Methods used in REST API Approach.

Refer blog http://findnerd.com/account/#url=/list/view/Methods-in-REST-approach/18130/