SOAP, or Simple Object Access Protocol, is a protocol used for exchanging structured information in the implementation of web services in computer networks. It relies on XML (Extensible Markup Language) as its message format and typically operates over HTTP or SMTP (Simple Mail Transfer Protocol). SOAP defines a set of rules for structuring messages, specifying how messages are formatted, transmitted, and processed between client and server applications. It provides a standardized approach for invoking methods or functions on remote systems, facilitating interoperability between different platforms, programming languages, and technologies in distributed computing environments.