What is the rating presented in the App Store?

Question

Does it show the average rating over a specific period of time? Or a cumulative average of all historical rating?

Answer 1

Per this thread from the Apple Developer Forums, it seems to be a source of much confusion for developers, however the default behaviour is described here, which states that the summary rating is specific to each territory and can be reset if the developer so wishes upon releasing a new version of the app

Answer 2

The rating is a cumulative average of all historical rating and segregated for each region (country/territory) app is sold in.

There is a minimum threshold of 5 reviews before the reviews and ratings are displayed to users.

For further details regarding App Store ratings and reviews, go through the support site set up by Apple, Ratings, Reviews, and Responses - App Store.