JailbreakQA is a community of volunteers answering jailbreaking and Cydia questions, and we think you might find the following information useful. You can also check out recent questions.
How do I fix problems that happen with using evasi0n7?
What is a jailbreak?
Jailbreaking your device means installing a small program that removes restrictions in the default software. A jailbroken device can run apps and extensions (themes and tweaks) not approved by Apple. Jailbreaking does not slow down your device or use extra battery, and you can still use all your existing apps and buy new ones from the App Store. Jailbreaking simply enables you to do more with your device; nothing is taken away.
Will evasi0n unlock my device? Does my device need to be activated before jailbreaking?
No, evasi0n does not provide a carrier unlock. (And if you're curious about the legality of unofficial carrier unlocks, see these explanations.) Yes, your device needs to be activated before using evasi0n.
What if I decide that I don't want the jailbreak anymore?
If you someday decide that you want to undo your jailbreak, you can plug your device into your computer, make a full backup with iTunes, click "Restore" in iTunes to wipe the device, and load your backup when prompted. All your App Store apps and the information in them will be preserved as usual.
Can jailbreaking "brick" my device?
Jailbreaking cannot put your device into an unusable state on its own. You will have full access to your jailbroken device, which gives you the power to modify it in ways that can put it in a state where you have to connect your device to iTunes and "restore" from a recently-synced backup. However, it should not be possible to render your device as permanently non-interactive as a brick, no matter what you choose to install.
Is jailbreaking legal in the United States?
We aren't lawyers, so we can't tell you for sure, but jailbreaking seems to be OK. A law in the United States, the Digital Millenium Copyright Act (DMCA), has an anti-circumvention clause which states that if there is a protection mechanism on a piece of software, a user is not allowed to bypass that protection. Jailbreaking may fall under that clause, but in 2012 the Library of Congress renewed an exemption for jailbreaking cell phones such as iPhones. A proposed exemption for jailbreaking tablets (such as iPads) was declined, but this doesn't necessarily mean that jailbreaking iPads is now illegal. It means that it's still a legal grey area - in other words, there's never been a DMCA exemption for jailbreaking iPads, and there still isn't one, but it's unclear whether the DMCA actually makes jailbreaking illegal in general. Jailbreaking iPod touches also falls into this grey area. If you are outside the United States, some countries have anti-circumvention laws with various exceptions and conditions, so please research the laws of your country to make sure jailbreaking is not prohibited for you - this may be a helpful place to start. Keep in mind that if you are pirating things, that is copyright infringement, which is illegal in most places.
Does jailbreaking void my device's warranty?
Apple says that they "may deny service for an iPhone, iPad, or iPod touch that has installed any unauthorized software," but jailbreaking is easily reversible, so you can go back to authorized-software-only whenever you want to. In other words, when you jailbreak your device, it is no longer eligible for Apple support if something goes wrong - but you can always restore the device to remove the jailbreak and then take the device into Apple for support, since a restored device has no evidence that it was previously jailbroken.
Does jailbreaking cause instability or battery drain?
Jailbreaking itself generally does not cause stability problems. But you have full access to your jailbroken device, which gives you the power to install software that can cause instability and even battery drain. If you're careful to install well-reviewed, popularly-recommended packages by reputable developers from legitimate repositories, you probably won't run into much trouble with crashes or increased battery usage. You do have to be willing to do a bit of research and troubleshooting though, since you're taking control and responsibility for your device and can install things that cause issues.
Does jailbreaking make my device less secure?
Having a jailbroken device is similar to having administrator power on your desktop computer: you have full freedom to install bad stuff on your computer, but you already know to stay away from installing dubious browser toolbars and sketchy email attachments - instead, you choose to install legitimate software from reputable developers. Use the same reasonable caution when installing software on your jailbroken device. It's generally a good idea to stick to installing software from the default repositories in Cydia (BigBoss, Cydia/Telesphoreo, Dev Team, ModMyi, and ZodTTD/MacCiti), only adding additional repositories if you really trust those additional repositories. If you're interested in technical details, check out this conversation with saurik.
What are some cool things to install after jailbreaking?
Check out the Featured lists in Cydia, and join the discussions in the Reddit community for jailbreaking.