The Task form can be for either a "Task" (ie something either you or someone else has to do) or a "Recall". There is not a great deal of difference at the end of the day, except to let you (and everyone else) know at a glance whether action is required.
If a Task, you should have the deadline date completed. If you want to be reminded before the deadline, put in a recall date. That is, you will have 2 dates, one for the deadline and one for a recall.
If a Recall, you only need the recall date.
Every time you review a Task form, you should put in a brief report. Do so especially when you extend or change the deadline or recall date. This provides a history of your conduct of the matter and makes it easier for someone else to understand how you have been handling a matter.