There are a few fundamental differences between REST and SOAP that you should know about. REST is a web service interface library that allows code to interface with an existing system of calls, while SOAP is a markup-based interface library that allows code to interact with an existing system of calls, and the reader can write code to manipulate the system.
REST is a more "normal" web service interface library, while SOAP is "wsabi" - that is, it is an interface that allows code to interact with an existing system of calls, but does not allow it to be written in the usual web Development Language. This is because SOAP provides an interface that allows code to call an existing system of calls, while REST does not.