Bungie announced those who pre-order Destiny from select retailers will receive a key for a beta that will launch in 2014. The beta is available for Playstation 3, Playstation 4, Xbox 360, and Xbox One. For those wishing to sample bits of the main game before it is released may want to jump onto the offer soon, as there are a limited number of beta keys available in a first come first serve scenario. You and your friends may want to act quickly if you want your entire team to establish a foothold on the world.
Participants will choose a retailer to purchase from who will provide codes for when the beta goes live. The exact date is unknown, but Bungie promises it will launch in "early 2014" and contain most of the activities in the finished product. The announcement has a pretty in-depth FAQ on Destiny's Pre-Order website if you want a full write-up. Those with enough faith in Bungie's ability to produce a quality product can go ahead and get their space wizard settled into their war torn home before it launches for real. It is unknown if you will be allowed to keep your beta character when the retail version drops, however.
Destiny's four player co-op and persistent world earned it a positive showing at E3 this year, and Bungie has certainly built up some potent street cred with their past Halo adventures. I hope that this is an effort to demonstrate a nearly complete game for loyal fans, and not outsourcing the testing for a complicated product.
Source: Destinythegame.com