Rating refers to a list of players who compete with you for valuable prizes during an event (festival). Ratings are available only during festivals, and for every festival, a new leader board with competitors is created.
You can see the rating leaderboard icon under the icon of the ongoing festival. It looks like a gold trophy:
Players are randomly divided into teams of 30 people.
How to earn rating points
Rating points (they look like coins, we also call them leaderboard points) are obtained through completing challenges on festival island (tap the challenges button in the leaderboard window to check current tasks).
Some islands might have a workshop where you can craft points.
Why would I want to compete for a high ranking?
Players in each group compete against each other. The goal is to get as many rating points as possible. Top-3 players will receive valuable prizes, but other players will also not remain without rewards. You can get time spheres, gold keys, gold bars and other resources as a reward for ratings.