relays see NIP-89
Does this sound right: it can either be: 1) an application that publishes (i.e. self-ceritifies) that it can handle a specific event/kind type, and/or 2) a recommendation from a user
yes and provides a URL (which could be a deep link) to handle the bech32, so when, e.g.. coracle, wants to open a specific event, it knows what URL to use to open that specific event on the app.