Simple Object Access Protocol (SOAP) is a messaging protocol that allows programs running on disparate operating systems to communicate with each other. Coursera's SOAP catalogue teaches you the fundamentals of this foundational web services communication protocol. You'll learn how SOAP can exchange structured information in web services interaction over computer networks, its application in distributed computing, and how it leverages eXtensible Markup Language (XML) for its message format. Dive deep into the structure of SOAP messages, the role of WSDL in describing the services available, and understand SOAP's specification and its ability to work over multiple protocols. As you master SOAP, you'll be well-equipped to design and implement robust and interoperable web services, crucial in today's interconnected world.