Yes. It merges that property's Airbnb, VRBO, and Booking.com calendars into a single feed.
In Airbnb, open Listings, pick the listing, then go to Calendar → Availability → Connect calendars → Export Calendar and copy the link. Airbnb gives one link per listing, so copy each listing separately.
In your VRBO owner dashboard, go to Calendar → Export Calendar and copy the iCal link.
In Airbnb, open Listings, pick the listing, then go to Calendar → Availability → Connect calendars → Import Calendar. Paste the link and give it a name.
In your VRBO owner dashboard, go to Calendar → Import Calendar and paste the link.
Yes. Export the link from each site, import it into the other, and a booking on one will block those dates on the other.
You still have to check each site separately, because neither one becomes a single combined calendar.
Yes. Connect your booking sites to CalBook once, and you get one combined calendar to follow in Google Calendar, Outlook, or your phone.
Use the "All except" export link for that site. It leaves out that site's own bookings so it does not re-import them.
Your connected calendars are checked at least every 5 minutes, so new bookings appear automatically.