Understand validations on record deletion
The 'Delete' event are the ones that are triggered when record is deleted. The 'Validations on record deletion' action will executed when you try to delete a record in the form. Do note that only the deluge scripts can be associated with this action.
Let's assume you have an Employee Management application. In that you have a Leave Request form that the employee uses while updating leaves taken or to be taken. The form includes the employee's name and ID fields, leave type field, date field, and reason field. The leave type field has Sick Leave, Vacation Leave, Personal Leave, On-Duty, and Maternity Leave as options. Once applied the leave request is assigned the 'Pending' status and then based on the decision of the manager the status is changed to 'Approved' or 'Rejected'. The employees also have the ability to delete the leave request which has been applied. But the company wants to prevent the requests with 'Approved' status from being deleted. This can be achieved by using the 'Validation on record deletion' workflow. You can write a deluge script that will trigger an alert box when status is 'Approved' and will also have cancel the delete request.