What is is a rule?
Every rule consists of three elements: trigger, input data and action.
The trigger is the event that will start to run the rule, e.g. a date or a completion of a sprint.
The input data is the basis you want to know more about, e.g. the code base of your project or the sprint backlog.
The action is what happens to give you the desired output, e.g. a code review or report for a sprint result.