Review score
A review score is the average of the ratings guests give you, usually on a five- or ten-point scale. It's one of the first things a prospective guest looks at, and OTAs use it to decide how high you rank.
Because it compounds, a strong score is worth protecting: it brings more visibility, which brings more bookings, which bring more reviews. Asking happy guests to review at the right moment is the simplest way to keep it climbing.