The rules module is a large project designed to take actions on certain triggers within Drupal. You can configure rules underneath Admin > Configure > Rules. Each rule takes the following format:
- Rules are triggered based on one or more events, such as node creation or node update.
- When the rule is triggered, there can be a series of conditions that must be met. Most data about the event is available for condition logic, and both nested AND and OR conditions are possible.
- If the rule is triggered and the conditions met, a series of actions are taken. These actions are extensive and include things like emailing a certain person or adding a node to a nodequeue.
For more information on exactly how you can use Rules, we recommend exploring it in your local site and seeing how it works. You can also check out the Rules documentation online: https://www.drupal.org/node/1299990.