Services are defined as independent pieces of logic which when placed together can be used to process many different types of business requirements.
Since services are not tied to web based applications this allows services to run when there is no response object available. This allows services to be scheduled to run at specific times to run in the background via the Job Scheduler.
The Service Engine allows you to invoke logic throught the engine. The Service Engine is responsible for:
located the implementation of the logic
determine the language it is writen
invoke the logic and obtain the result