Turn this on for daily or recurring monitoring of the same city/locality/URL search. The first run returns all matching properties as NEW. Later runs normally return only NEW, UPDATED, and REAPPEARED properties -- a property is UPDATED only when its own listed details change (price, title, area, amenities, images, etc.); the scraped_at timestamp is ignored for this comparison since it always differs run to run by construction (every returned property still carries its current scraped_at value). Turn on "Emit unchanged" or "Emit expired" only when you also want those properties returned (and billed). State is kept separately for each city/locality/service or URL set and filter combination; use State key when you want to name or deliberately share a monitoring campaign. To continue one specific interrupted run instead, use Resume from a previous run above.