Trackers can be triggered by either a Task change or an Opportunity Cron Job.

The Opportunity Cron Job runs at the frequency that you select (Daily, Weekly or Monthly) and allows you to create automations based on Opportunity and Account level criteria.

The reason this runs on a Cron is because very often analysts want to detect the absence of an event (eg: an opportunity hasn't been updated in X days, or opportunity age has reached a certain level). Because there is no trigger for these measures, they have to run in a batch process.

The most basic tracker settings include, Tracker Name, Description (what the Tracker does), Category (for categorization) and Priority.

Priority allows you to assign an order in which Trackers are executed, allowing you to chain logic in a specific flow.

For example, you may want to have one tracker that increments an object field (eg: risk score) and then another that fires once that object field meets a specific threshold. Priorities execute in ascending order, so #1 is always executed first.