You can optionally enter comments on the work item page. Comments can be viewed by trackers of the workflow and by participants at subsequent steps who are allowed (in the workflow definition) to view workflow history or status.
To enter a comment:
Although you can enter more than 500 characters, after you complete the work item only the first 80 characters will be visible (via the History page or the Step History tab in the Process Tracker window). The entire comment is visible not only as you enter it, but also if you: