Upon opening the application, you will soon see that AppBrain App Market is a 'market' of applications whose identifying features are functionality and transparency.
Functionality, because from the application it is possible to access the files of Google Play or even download other applications that you find interesting, and because you have dozens of options to filter and find the applications in which you are interested.
And because AppBrain App Market transparency promptly informs you all the details about an application, such as permissions you can grant, and the prices as which it has previously been (if it is a paid app).
Besides all this, AppBrain App Market allows you to register with their service to benefit from both the ability to download applications directly, and the opportunity to participate in the community.
AppBrain App Market is one of the most interesting alternatives we can find to Google Play, and definitely the closest thing to an Android AppShopper that exists today.