Web Services Description Language (WSDL) is an XML-based file format used to describe the technical details and functionality of a web service. It serves as a formal contract between a service provider and a service consumer, detailing the specific operations available, the input and output message formats, and the network protocols required for communication. A WSDL file typically defines the service's endpoints, the data types used (often via XML Schema), and the binding information that maps the abstract interface to a concrete protocol like SOAP (Simple Object Access Protocol) over HTTP. By providing a machine-readable specification, WSDL allows developers to use automated tools to generate client-side proxy code or server-side stubs, significantly simplifying the integration process between disparate systems. It is a cornerstone of traditional Service-Oriented Architecture (SOA) and remains a standard for enterprise-level SOAP web services, ensuring that different applications can interact seamlessly regardless of the programming languages or platforms they are built upon.