Apex Web Service Integration

Apex provides integration with Web services that utilize SOAP and WSDL, or HTTP services (RESTful services):

You can expose your Apex scripts so that external applications can access your code and your application. To expose your Apex scripts, use the WebService Methods or SOAP Services: Defining a Class from a WSDL Document.
You can access external Web services using Apex. The services can use either SOAP and WSDL, or HTTP services, also called RESTful services. For more information, see HTTP (RESTful) Services Classes.