Rules within a folder are prioritized numerically, with the lowest numbers given the highest priority. By increasing the priority of a rule, you increase the likelihood that content displays if there are other rules with overlapping trigger criteria.
For example, you have two rules in a folder with these settings:
A "Digital Cameras" page that is set to trigger at the refinement state Cameras > Digital Cameras and allowed to display at any location that matches Cameras > Digital Cameras
A "Digital Cameras from Canon" page that is set to trigger at the refinement state Cameras > Digital Cameras> Canon and restricted to display at only that exact location
If you prioritize "Digital Cameras from Canon" as a "1," and "Digital Cameras" as a "2," then"Digital Cameras from Canon" will always be evaluated first. That means that even though both pages could display to a user who navigated to Cameras > Digital Cameras> Canon, only "Digital Cameras from Canon" will display. The Digital Cameras" page still displays at any other location where a user navigates to Cameras > Digital Cameras, but it will always be evaluated after the more specific "Digital Cameras from Canon" page.
If, however, you were to prioritize "Digital Cameras" before "Digital Cameras from Canon," then the page "Digital Cameras from Canon" would never display in your application. It is important to make sure that more specific pages (pages with more complex triggering criteria) are given high priority to prevent them from being blocked by more general pages.