It may not look like, but it's one among them... 'Business Rules' is also a type of Workflow.

CRM 2013 introducing a simple declarative interface to help you implement and maintain your fast changing, commonly used business rules. You can do client side scripting without knowing anything about JavaScript.

Have you ever wondered how the business rules are stored in CRM ? Have you ever thought 'Business Rules' are also one of the Workflow category?  Even though they may not look like, but they are one among them. Yes, 'Business Rules' is also a type of Workflow.

Below is the screenshot of the Workflow category in CRM 2013. As like others Business Rules (PBL) details are also in Workflow Tables with Category = 2