Conditional Alerts
A Conditional Alert is similar to a Broadcast in that you are sending content to recipient(s) on a specific schedule. The main difference is that for broadcasts the system only ever creates one instance of the schedule you define, and with conditional alerts the system creates an instance of the schedule for each open case that matches the given rule criteria. Conditional Alerts are designed to create an instance of the schedule you define every time the rule's criteria go from being False to being True for an open case. That could mean that the rule is being run for the first time and it matches a case, or it can mean that a case which didn't match the rule before is later updated to match it.
Before continuing, make sure that you are familiar with the concepts of Case Management
Here is video that shares an example of an app using conditional alerts.