What is Jailbreak?
Jailbreaking your iPhone is a process where you open up your iPhone (not literally) to a lot of options for customization, apps, and control. By default, a lot of features in iPhone are not controllable.
For instance, you cannot change the color modes or profiles of your iPhone. These can be done through a jailbreak. The basic idea is to jailbreak the iPhone to include repos like Cydia where you get hundreds of thousands of apps which are not available on the iTunes App Store.
Is Jailbreaking Safe?
Jailbreaking is actually safe. It does not break your iPhone, for sure. If there are any risks, it is only through the apps that you download. Even here, the risk is quite little because most of the apps on the Cydia repo (the default jailbreak repo) are quite safe, popular and community-driven which means you'd get to know if an app is good or bad.
Jailbreaking opens up quite a lot of possibilities to your iPhone:
1. To begin with, you get access to much more apps than iTunes App Store. The reason this is advantageous is because many of the apps cost you a lot on the iTunes App Store. On a jailbroken iPhone, you get access to a repository which has thousands of similar apps which are either free or very cheap. Not to worry too, these apps are not sub-standard in quality they are equally good and awesome.
2. Customization is something that we all like. Yes, there are quite a lot of apps for that but Apple doesn't allow them to be sold on iTunes App Store because it's against their policy. That's where jailbreaking helps. There are literally countless apps for customizing your iPhone the way you want and these can be had and used only if you jailbreak you iPhone.
3. Jailbreaking gives you greater control over a lot of other things on the iPhone. Not just themes, apps and settings but you can get deeper into the iPhone and if you are someone who's a bit of a geek you can also make umpteen numbers of changes to the system.
4. Jailbreaking helps in making using of 3G facilities better and in fact, when FaceTime could be used only via Wi-Fi, jailbreaking apps let you make FaceTime calls via 3G too! This was a great advantage for those who did not have Wi-Fi setup or people who were out of Wi-Fi networks.
So, as can be seen, there are quite a lot of advantages of jailbreaking. It's easy these days. You can jailbreak your iPhone through many ways including Wi-Fi. All this said and done, you need to be careful with the apps you install on your iPhone via jailbreak.