Adding Workflow rules to your system helps coordinate activities that occur in your business.
An example could be that "Purchases above $5000 require approval by a manager".
Workflow is built on Notifications that are setup in your system.
There are two ways of creating Notifications:
1. Visually Defined Notifications can be setup using simple criteria.
2. Coded Notifications require you to add source code to your system that is run periodically to check for actions that need to be taken.