Podping is a global message bus for podcast infrastructure events. Entities that publish feeds can "write" events into the system and those events are then visible to all parties who "watch" for them. Anyone can watch/monitor for events and respond appropriately, depending on their needs.
Podping uses the Hive Blockchain as a permissionless, open database: anyone can write podpings and all podpings can be watched by streaming the Hive blockchain and watching for "custom_json" operations which have a specific ID (anything starting with "pp_").
It was developed as an alternative to WebSub and rssCloud which both have major drawbacks when it comes to podcasting infrastructure.