How to understand that SOAP webservice use HTTP only for transport?

As I understand RESTful webservices use whole power of http, suffice to say all that rest need is http, but in the same time rest!=http. CRUD provides ability to do any action with API resourses, for example we send http request, this request has header for aunthefication, name of method (for example put), and json in body for updating. How this proces is running via SOAP? SOAP uses XML, but how this XML is delivered to API?