Service Oriented Architecture is not a new development and has existed for over a decade. It was earlier done with the use of DCOM or Object Request Brokers (ORBs).
The services offered by SOA are loosely interconnected and are ideally independent of each other. In simple words, over here, the implementation interface is completely independent of the service interface. Hence, the applications can be built by system integrators without any prior knowledge of the service implementations. In SOA, all that the system integrator needs to possess is the skill set to compose one or more services aptly. A suitable example of this set up would be an application implemented in .Net and the application which is consuming this service is running on a completely different platform and perhaps even a different language