Let me give you an answer: WebService, SOAP, UDDI, etc.

Web Soap is just a protocol, a simple xml-based protocol for exchanging structure and type information on the Web, from its name (soap, Simple Object Access protocol, easy object Access Protocol) You can see that the purpose of the design is to make the information exchange as simple as possible. SOAP is just a framework that can be implemented as a carrier of HTTP, or through other such as FTP,SMTP or even a floppy disk, but it is common for HTTP protocols to be used, so it seems to give the impression that soap must be based on HTTP. In addition, since SOAP is a protocol, it does not mean that it must serve the webservice.
As for the 2 modes of SOAP with RPC and XML HTTP, this is not true, first soap is xml-based, and RPC call is done via HTTP, and the following is a SOAP request called "echostring" RPC method calls:
Post/test/simple.asmx http/1.1
host:131.107.72.13
Content-type:text/xml; Charset=utf-8
Content-length:length
SOAPAction: "Http://soapinterop.org/echoString"

<?xml version= "1.0" encoding= "Utf-8"?>
<soap:envelope xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance"
Xmlns:xsd= "Http://www.w3.org/2001/XMLSchema"
Xmlns:soapenc= "http://schemas.xmlsoap.org/soap/encoding/" xmlns:tns= "http://soapinterop.org/"
xmlns:soap= "http://schemas.xmlsoap.org/soap/envelope/" >
<soap:body soap:encodingstyle= "http://schemas.xmlsoap.org/soap/encoding/" >
<tns:echoString>
<inputString>string</inputString>
</tns:echoString>
</soap:Body>
</soap:Envelope>
As you can see, the method name echostring is included in the SOAP body.