We can define reminders to be triggered before, after or at the time of the event, to the person whom the Task is assigned to.
To set reminders,
>> Go to Workflow through the left menu.
>> Go to Workflow Management.
>> Select the Workflow for which the reminders need to be set.
>> Select the Task in edit mode for which reminder needs to be set.
>> Tick on Set Task Duration.
>> Click on Add Reminders. Reminders can be set for Hours, Days or Weeks and can be selected to trigger Before, After or at the time of the Event.
Multiple reminders can be set for a Task.