Service Oriented Architecture or SOA is a design pattern. It is designed to provide services to other applications through protocol. It is a concept only and not tied to any programming language or platform.
Web services is a technology of SOA most likely.
A service is well-defined, self-contained function that represents unit of functionality. A service can exchange information from another service. It is not dependent on the state of another service.
The figure given below illustrates the service oriented architecture. Service consumer sends service request to the service provider and service provider sends the service response to the service consumer. The service connection is understandable to both service consumer and service provider.