Well... Jailbreaking Is a method used to add so called "Cydia" to your applications, it is like the AppStore except more open sourced and more variety of themes, customization, tweaks, transitions, wallpapers, ringtones to change... Although many people say "it has ruined my device" it's well them ruining their device because they instal everything they see... Which isn't safe... So just to point out "Do not instal everything you see!" Look via YouTube or other websites that tell good info about It and then later decide wether or not to download it... Hope this helped!