Beta Software
Any piece of beta software, whether it's a game, a website or a simple computer program, is software that's still in testing but available for use. Practically every piece of software has a "beta" stage, but typically only the developers use the software then; only sometimes will they release it to the public or a select group as well. Typically, the software will have deficiencies and errors in it, so users shouldn't judge the final product on any weaknesses of the beta. All this "beta testing" is to help prepare for the official launch of the product. One reason developers release beta software so they can locate and correct errors more easily; with hundreds or thousands of people using the software, certain obscure issues may be easier to isolate than when just a handful of developers test it. Also, developers have the opportunity to address comments users make, even if they are not regarding errors. Users may find certain portions of the software confusing or difficult to use, and beta testing a product allows developers to find these issues and fix them before an official launch. Reputable developers never charge for the use of a beta product.
PS3 Beta Games
A beta game on the PS3 console is just a game that's available for the PS3 before launch and may have some errors or problems still in it. Usually, there's no difference between a "beta" game and a "demo" game except the "beta" term warns that you should expect some problems while using the game, while a demo is usually much more refined and is often only available at or close to the game's full launch. Also, game demos are usually available for an extended period of time or even indefinitely, and a beta game is usually available for a narrow window of time, sometimes just a few weeks. A beta game can still be enjoyable to play, and you get a taste of what's to come so you can find out if you're interested in buying the final product.
Popular PS3 Betas
Some of the most well-known betas for the PS3 are among the console's exclusives. Naughty Dog released multiplayer betas for "Uncharted 2: Among Thieves" and "Uncharted 3: Drake's Deception," and Media Molecule released betas for its popular titles "LittleBigPlanet" and "LittleBigPlanet 2." The second and third entries in Insomniac Games' "Resistance" series have had multiplayer betas as well. Ubisoft Montreal released "Assassin's Creed: Revelations" in beta form on the PSN in preparation for their fourth major game in the series.
Finding a Beta Game
Beta games are available often on the PSN as a free download, just like a game demo. Occasionally, beta access is restricted to the first people who sign up for it online or to those who purchased another game, such as the initial availability of "Uncharted 2;" only people who bought "Infamous" had access to that beta, though later it opened up to everyone on the PSN. If a beta has a smaller availability, sometimes the developers will open it up to more people later on, but not always. Every case is a little different, so if you're interested in a specific beta game, you should check the PSN regularly for it and look for information about it at the developer's site and at gaming websites.