Shopify's default best-selling sort only shows products according to sales over the lifetime of the store, so there's no recency or seasonality to the algorithm. 'Rank King: Best Sellers' allows you to better capitalize on your trending products by showing best selling products according to a specific time frame such as the last 7 days, this week, this season, and more. It also allows you to rank best sellers according to number of orders, total quantity sold or by revenue generated.