Jailbreaking your phone means that you hack into the system to remove limitations on your iPhone. People do this when they want to upload apps that are normally not allowed via Apple apps or otherwise modify the way their phone looks or operates. This is a controversial activity because it breaks the Terms of Service agreement and voids the warranty. However, others feel that by restoring the iPhone and removing any evidence that it was jailbreaked will make it impossible for Apple to tell if you had broken the Terms of Service.

Jailbreaking is also controversial because some say it will break your iPhone, although others disagree. Those who disagree feel that if needed you can always restore your iPhone to correct any issues that jailbreaking may have caused. Keeping the controversy in mind, whether you proceed to jailbreak or not is up to you to decide if it’s worth it to take the risk because there will be no warranty support available if you are unable to restore your phone and remove evidence that you had hacked into the system.

Resource: iJailBreak