App Rankings can reference how an app ranks in a search from the store. It can also reference the over all app rankings from the store, based on downloads and revenue.

You can view App rankings on Top Charts Page.

The Google Play Store and the App Store categorize apps into categories that users can browse through lists. An app's position in each list is known as its "category ranking."

FoxData Category Ranking page provides information about app's rank in the stores

For you have any other questions, please check out the link: Product Feedback