Workflow interface defines the workflow. Impl class provides implementation.

A worker needs to be created with worker factory (with task queue name), register workflow implementation.
Then worker needs to be started. This will result into worker start polling task queue (which is maintained at server) 
and acting on it if any workflow work gets started.

workflow starter - creates a workflow with workflow options (options like task queue name, workflow id).
After that desired work can be initiated. With this queue will have a work registered, which will be picked by worker