I still don’t fully understand it even though I’ve had it explained to me at least one other time
What makes you excited about it?
Discussion
It is a way for two relays to know which events one has and the other doesn’t, so that you can sync them.
You can use a local relay / cache and keep it in sync with your actual relays easily. And it’s super fast!
If using JS, take a look at @welshman/net for a good implementation.