Instant rentals is a feature that allows renters to book immediately without your approval of the dates. When setting up instant book, you will set the number of days within the start of the trip, that you will not allow a renter to book. This allows you to have notice of the rental. Entering your bank account information under the payout settings and keeping your calendar up to date and current are requirements of enabling instant booking.
If you do allow instant booking, please make sure to stay active on the site so you know when your RV has been booked.