SOAP is a way for a program running in
one kind of operating system to communicate with a progam in the same or
another kind of an operating system by using the World Wide Web's
Hypertext Transfer Protocoland its Extensible Markup Language as the
mechanisms for information exchange.
While REST stands for Representational State
Transfer, which is an architectural style for networked hypermedia
applications, it is primarily used to build Web services that are lightweight, maintainable, and scalable.