Up until now, coordinating multiple processes required inter-process communication (IPC) mechanisms that were intrusive and non-straightforward. TaskGarden does all of these for you behind an easy to use interface. From your point of view, it's just like writing a sequential program.
Worker processes are created on the fly. They will then listen for requests from the host process. By loading the .NET assemblies that are loaded by the host process, the worker processes can execute the code referenced by the host.