We just want all things in one place. So aa in case of android apps. Google Play store is a market or rather a mall of all Android apps taken together. All aaps registered here are genuine and contains no virus or malewares. One can even write a comment for improvement of the app and even rating facility is also there.
Option of user reviews provide true information of apps to the downloaders before downloading them. downloadingof specific apps are free, One can ever can buy e-books and movies from the play store.