What are Idempotent and Safe methods of HTTP and REST

In order to efficiently work with REST and RESTful web service, good knowledge of HTTP is really helpful. Even though REST seems easy, designing a uniform and consistent RESTful API is a tough job. One of the tricky tasks is choosing right the HTTP method for right job e.g. when to use PUT vs POST. Once you know the meaning and purpose of different HTTP methods, it helps to choose the right method for the right job. You can divide HTTP methods into two main categories safe and idempotent. Safe methods are HTTP methods that do not modify the resource e.g. a GET request  is safe because it doesn't modify the resource you are requesting e.g. data of a Book. Another safe HTTP method is HEAD, which doesn't change the resource representation on the Server, but all other HTTP methods e.g. POST, PUT, or DELETE are non-safe.

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