SOAP is a network protocol and is regarded as standard
SOAP is an abbreviation for Simple Object Access Protocol and was developed by DevelopMentor, IBM, Lotus Development, Microsoft and Userland Software. It acts as a network protocol, enabling data exchange between systems, and remote procedure calls can be made. The main developer is Don Box from DevelopMentor, one of the specialists of XML. SOAP is now a standard supported by the W3C Consortium. SOAP is a standardised protocol packet for exchanging messages between on distributed system in web service technology. This specification defines a simple XML based environment, the so-called envelope, in order to exchange information and a set of rules to transfer applications and platform-specific datatypes in XML representations. SOAP is designed so that it can represent a wide variety of use cases.
SOAP is based on XML and HTTP
Each SOAP message is an XML document, which consists of three segments: the SOAP envelope, the SOAP header and the SOAP body. While the SOAP header is optional, the two elements SOAP envelope and SOAP body must be present in every SOAP message. SOAP is an XML-based protocol and is based on two existing standards. HTTP which transports the message, and XML which acts as an envelope for the message.
SOAP is based on XML standards like XML schemas and XML namespaces. A SOAP application should also include the namespaces provided by SOAP for all elements and attributes. In addition, an application for processing SOAP messages should be able to recognise all elements from the SOAP namespace and to discard messages that have incorrect namespaces.
SOAP’s goals are simplicity, expandability, the use of distributed systems even through firewalls and the use of current standards like HTTP and XML.
You can find more information on SOAP on Wikipedia: https://en.wikipedia.org/wiki/SOAP