Before I begin, let me clarify ahead of time that this thread isn't intended to be a tell-all guide on every nuance of the current PS3 Jailbreaking scene. The purpose of this thread/guide is to answer some of the most commonly asked questions. Others more knowledgeable than myself have already created threads on the various ports, uses and Jailbreak methods. Having said that, let's begin.
Q: What is this whole Jailbreak thing about? What's it for? Do I need it?
A: The Jailbreak is what's known as a heap overflow exploit, performed by a combination of software and a custom USB device, that sends the PS3 into a state that allows for unsigned code to be installed and ran. The overall purpose of the Jailbreak is to allow for homebrew applications to be used on a retail PS3, similar to how Debug/Test units run. It does NOT turn your PS3 into a full Debug unit. While game backups are the primary focus of most Jailbreakers, overall the potential for opening up the PS3 is limitless at this point. As for whether you need it or not, that's entirely up to you to decide.
Q: I've read where Sony is shutting down resellers of the different Jailbreak devices. Isn't the Jailbreak legal? Should I be worried if I buy/create/use one?
A: The short answer is, no one is sure just yet. Buying, selling and distributing a ready-made Jailbreak solution (such as PSJailbreak, X3Jailbreak) is illegal in many places. However, buying or owning a "blank" device that can conceivably be used for Jailbreaking is not, such as the Teensy ++ or BlackCatUSB. Right now, until more outcomes from Sony's various lawsuits are known, it's a pretty large grey area. So your best bet is, proceed with caution. Banning from PSN is a very real possibility, and the potential for Sony to sequester your ISP and obtain your information to initiate a lawsuit, should you download a pirated game off BitTorrent or elsewhere is also a firm possibility. So overall...use at your own risk.
Q: Will the Jailbreak work on <insert device name>? When will there be a version of it for my device?
A: Right now, everything is in the very very early stages of life, so there is no definitive list of what devices can and can't be used to perform the Jailbreak. While a number of ports are currently being worked on (Android, N900, etc), no one can tell you for sure, when, or even if the Jailbreak will be ported to your device, or if it's even feasible. Your best bet? Give it time. As I said, the Jailbreak was announced less than a month ago, and reverse engineered less than a week ago. Projects will come and go...some people may give up when they realize it's too daunting a task to port the JB to a certain device, while others may pick up where they left off. The Search function, both here and on Google, is your best friend.
Q: I see someone selling a Jailbreak for <insert amount here>. Should I buy it?
A: That again, is entirely up to you. Its your money, and if you absolutely MUST have a Jailbreak and have zero tech experience or know-how, buying a ready made PSJailbreak or clone, IF you can find one, may be what suits you. Many others are either ordering cheaper blank solutions to program themselves, or are waiting for low-to-no cost solutions (such as a PSP port). It's your choice, though I would personally recommend waiting a few weeks. It's taken four years to crack the PS3... a few more weeks won't hurt you, and may save you a ton of cash and headache in the end.
Q: Will I go to jail for using the Jailbreak?
Q: Will I be banned from the PlayStation network for using a Jailbreak?
A: Yes, more then likely.
Q: Is there any way to prevent from being banned?
A: Yes. Don't buy a Jailbreak. Otherwise, there is no clear cut way to prevent from being banned.
Q: What's this PS3 SDK I keep reading about? is it legal? Do I need it, too?
A: If you have to ask, then no, you don't need it, and it is most definitely NOT legal. The SDK (Software Development Kit) is for developers and homebrew authors.
Q: Anything else I should know?
A: Yes. CYA (Cover Your A$$). No one is going to bail you out should you get in over your head. Right now, the entire Jailbreaking scene is a potential risk to both yourself and others. Don't give up hope, though. Once the dust settles, the Jailbreak scene will be just as commonplace as any other game system homebrew/piracy. A great time for PS3 owners is right around the corner!