Most vacation rental property owners do not want to operate their business like a hotel, where guests stay one night, and there's a new guest the next day. Generally, you want a minimum stay of 2 or 3 nights, and potentially longer during holidays and high seasons. Some owners have minimum stays of a whole week. This can be set in the Rules for each property, or in a Season:
It's pretty obvious what the first three lines are for - minimum nights required for a booking in the various cases. What's the gap nights for, though?
Leaving Money on the Table
Consider a property with a 1-week (7 night) stay requirement. It's easy to imagine a booking that looks like this:
We see that this booking, in blue, is 8 nights - no problem. There's another booking that ends 2 days before, leaving one empty night in between - no big deal.
But then, there's another booking that checks in on the following Saturday. That leaves 4 empty nights in between. That's less than the 7 night minimum, so the booking engine will not allow anyone to book those days. The property will just sit empty.
Seems like a shame, doesn't it? Too long to not care, but too short to fit in the rules.
Filling Up The Gaps
That is what "Minimum Gap Nights" is intended to address. You can set a special absolute minimum booking length, that will only be applied inside of a gap that would otherwise be too short to allow a booking at all.
So, what would happen in our example with a Minimum Gap Nights setting of 2?
The gap from Jan 13-14 is only one night, so no booking would be allowed there even though it's a gap.
But now, the gap from Jan 22-26 is bookable, because it is longer than the Min Gap Nights of 2! The booking engine, for just these dates, will shorten the required minimum stay length to the size of the gap - in this case, 4 nights. A guest would be allowed to make a Jan 22-26 because it's in a gap, when otherwise that would not have been allowed because it's too short. Found money!
Don't forget that the Seasons settings can override the Property Rules settings, in either direction. So you can have a general Min Gap Nights setting of 4 in your Property Rules, a Min Gap Nights setting of 6 in your High Season when you don't want short bookings at all, and a Min Gap Nights setting of 1 in your Off Season when you'll take anything you can get.