Service Oriented Architecture
Service-oriented architecture covers application-specific touch points with business-oriented interfaces, provides decoupled design, agility, reusability, maintenance savings, and has become the architecture of choice for IT integration.
SOA is not a technology. It is an architectural approach built around existing technologies. SOA advocates a set of practices, disciplines, designs and guidelines that can be applied using one or more technologies. SOA encourages developing services around existing business functions offered by an application. Other applications that need communication with this application make use of one or more services to accomplish the desired business task.
Service-oriented architecture is about building standard interfaces to access business functions that are exposed by core business systems. But it is also about orchestrating existing functionalities across business systems.