SOA or Service-Oriented Architecture is an architectural approach to organizing software and other capabilities in the form of a network of services.
The services may be rendered in the form of web services, and may comply with various standards and protocols including WS*, but this is not essential to the concept of SOA. What is essential to SOA is an architectural approach, which is what distinguishes SOA from JBOWS (just a bunch of web services).
Many computing vendors provide tools, platforms and other infrastructure to support SOA. However, SOA is more than just these products. SOA should be thought of mainly as the set of architectural and development practices needed to use these products effectively.
Proponents of SOA believe that a loosely-coupled, layered service architecture can provide a combination of efficiency and flexibility.