The Public Beta Environment (PBE) is a limited-access public League of Legends realm where players help us test "declassified" features, content and experiments that aren't yet (and may never be) ready for prime time.
Riot's mission is to be the most player-focused game company we can be, and part of that is making sure that we're taking cues from you. Your feedback is what fuels us as we strive to make the League experience better. When it comes to rooting out problems, testing ideas, and building the game, the more feedback from you we can get earlier in the process, the better off we're gonna be. The PBE lets us call up a bunch of passionate League of Legends players to get their eyes, brains and QWER keys in front of cool new stuff while it’s still being worked out.
Periodically, we’ll invite a small group of tester applicants (selected based on a variety of criteria) to test out upcoming features and content for a specific PBE cycle. Invited testers then get to create a PBE account, download the PBE client and play. For the time that testers have PBE access, they’ll be able to test and provide feedback on upcoming champions, features and other content in order to help make sure it’s ready for release.
After each PBE cycle ends, testers will be returned to the pool of applicants, from which we'll draw a fresh group of testers for the following cycle. We do this to ensure we're choosing the right testers for the right features as well as to increase the number of voices that influence the direction of League of Legends.