The "Royal Club" frequent flyer program is not a widely recognized program associated with a specific airline as of my last knowledge update in September 2021. Frequent flyer programs typically have distinct names tied to specific airlines, like "Qantas Frequent Flyer" for Qantas Airways or "Miles & More" for Lufthansa.
It's possible that a new program with the name "Royal Club" has been introduced by an airline or travel company since then, but I do not have information on any developments beyond that date.
Frequent flyer programs are designed to reward loyal customers who frequently travel with a particular airline. Members of these programs earn miles or points for each flight they take with the airline, which can later be redeemed for free flights, seat upgrades, lounge access, or other travel-related benefits.