What is the difference between a SOAP API and a REST API ? Which one is mostly used in Salesforce?

Hi Hariom,

• REST API has no official standard at all because it is an architectural style. SOAP API, on the other hand, has an official standard because it is a protocol.
• REST APIs uses multiple standards like HTTP, JSON, URL, and XML while SOAP APIs is largely based on HTTP and XML.
  As REST API deploys multiple standards, so it takes fewer resources and bandwidth as compared to SOAP that uses XML for the creation of Payload and results in the large-sized file.
• The ways both APIs exposes the business logics are also different. REST API takes advantage of URL exposure like @path("/WeatherService") while SOAP API use of services interfaces like @WebService.
• SOAP API defines too many standards, and its implementer implements the things in a standard way only. In the case of miscommunication from service, the result will be the error. REST API, on the other hand, don't make emphasis on too many standards and results in corrupt API in the end.
• REST API uses Web Application Description Language, and SOAP API used Web Services Description language for describing the functionalities being offered by web services.
• REST APIs are more convenient with JavaScript and can be implemented easily as well. SOAP APIs are also convenient with JavaScript but don't support for greater implementation.