Rules module can do so much stuff, it can be overwhelming. In my own site building, there have been many times when I've written code to accomplish something, only to go back later and find out "Oh, I could have just done that with Rules". If you can write the code, sometimes that's better for various reasons, but if you're not as comfortable writing code, or if you already have Rules running on your site, you should absolutely learn how to use it better.
We'll go over the basics of what Rules module is and why you might already have it on your site (e.g. if you're using Drupal Commerce or Ubercart, or if you're a time traveller from the future when Rules has successfully made it into Drupal 8). We'll walk through a couple of things you can do with it, including building a notification system that's lighter weight than, say, Notifications module.