While editing the Workflow, it is possible to make it so that Users will receive an email when changes are made. 

Procedure

1. Click on the Modules tab in the upper left of the screen. 
2. Click on the name of the Module containing the workflow you wish Users to receive email notifications for. 
3. Click on the Workflows tab. 
4. Click on the name of the Workflow you wish to modify. 
5. Click the Action tab (or Next twice). This should take you to a page titled Process Flow- User Actions. 
6. Click on the name of the Action to edit that you wish Users to be notified for (e.g.: Submit). 
7. Check the Notify Users Via Email box. 
8. Optionally, check Requester, Assignee, Submitted By, or Modified By to make it so that the respective User who performs these actions is notified via email. 
9. Or fill in the blanks for Specified Users, Roles, Email External Recipients, and Custom Recipients based on who you want to notify. 
10. Click Save at the bottom of the page.
11. Now when the workflow Action you updated is triggered, the recipients you have specified will receive an email. 

Note that you will want to specify email content, too, see this topic: How do I customize email notifications?