Activity - Task
A task or activity is description of a piece of work that forms
one logical step within a process.
An activity may be manual or a workflow (automated) activity.
An activity is the smallest unit of work which is scheduled
by a workflow engine during process enactment; one activity
may result in several work items being assigned.
A resource performs the work represented by a workflow
The work usually consists of one or more work items assigned
to the workflow participant via the worklist.
Workflow Participant - Resource