While it has been possible to sideload beta versions of apps on your Android device, it usually involved downloading them from the developer website or through some Google+ group. With the latest Play Store update, however, things are about to get a lot easier for those who frequently install beta apps. To take advantage of these features, you will need to sign up as a beta tester. You will get a prompt when you open Play Store and you can accept to become a beta tester. Once you do that, you will see beta apps on the store. These apps will be clearly marked as (Beta) at the end...
Source: http://www.gsmarena.com/play_store_update_improves_beta_download_experience-news-18242.php
