The ExecutionType shows whether the task is synchronous or asynchronous. When a GeoprocessingTask is set to synchronous the results of each operation are returned to the client as soon as the operation is complete. An asynchronous task typically takes longer to execute and a job ID is returned to the client. The client can then use this ID to retrieve the results at a convenient time. An asynchronous service also gives you the opportunity to get feedback on the job status of the asynchronous operation. Synchronous services are intended for geoprocessing operations that take a short amount of time to execute, while asynchronous services should be used for longer-running operations.