Hello Sameer,
content types and aspects are relevant, when you want to distinguish following differences
* different sets of metadata
* different sets of edit-forms in the details page or workflowsteps
* different configurations (icons, searchabilit, beahviours, rolerights, actions)
To do a workflow with workflowrelevant metadata with 1 or more files, you do not need contenttypes in the standard explorer at all. You do need a workflow-contentype to enable the workflow to store its data somewhere.
The advanced workflow is basically a token, passed around between actors (the system or a javaclass could be an actor as well, then its not a "tasknode but just a node". Each user gets displayed a specific edit-form based on the workflow-contentmodell and the web-client-config.properties and web-client-custom-config.properties.
So you can pass files to be edited (content or their properties) or to enter data in forms during the workflow and act upon that.
Does that help ? For further readings, check the wiki for "Workflow adminsitration" and the links in my signature.
Norgan