Definitions

A WSDL document defines services as a collection of network endpoints or ports, where the port types are abstract collection of operations, and the concrete protocol and data format specifications for a particular port type constitutes a reusable binding.
Types: a container for data type definitions using some type system such as XSD.
Message: an abstract, typed definition of the data being communicated.
Operation: an abstract description of an action supported by the service.
Port Type: an abstract set of operations supported by one or more endpoints.
Binding: a concrete protocol and data format specification for a particular port type.
Port: a single endpoint defined as a combination of a binding and a network address.
Service: a collection of related endpoints.