The focus of this chapter is WF4 tracking and persistence. In the old WF3, we usually call them as services. In WF4, these features are implemented as extensions. The term "service" in WF4 usually refers to WCF service.
The Tracking extension in WF4 can record the "foot prints" of the execution of a workflow instance. The Persistence extension in WF4 can save running workflow instances in durable storage such as a database or disk file.