As found in their Genius Program Guide, Booking.com explains that the Genius Program is a marketing tool for selected properties to gain extra exposure.
Properties in the Genius program "Receive extra visibility through special tagging and dedicated Genius sorters and filters... to stand out among other properties in the same area and drives more traffic to their property pages, which may increase conversion rates, occupancy, and incremental revenue all year."
What do I need to do to join the Genius program?
Reach out to your Connections Specialist through any of these methods, and let them know that you're interested in the Genius program.
They will review your property based on Booking.com's criteria and let you know if you are eligible to join the program.
If your property is eligible, your Connection Specialist will reach out to confirm the program details before you are officially enrolled.