Jailbreaking is the modification of your Apple iOS with another software that overrides limitations on the iOS. No physical damage is done to your device as long as it is done sensibly. It is advantageous since it allows one get themes not found in Apple store (while still granting one the ability to use Apple store). It increases security since one can change root access passwords which all have a default that is similar in almost all types of an Apple product (eg the iTouch). It allows one expand the functionalities of an Apple product. For example, before iOS 4 came out, jailbreaking users already had been enjoying the ability to integrate twitter in their iOS, switch wallaper and themes and even integrate services like Google Play etc. Jailbreaking rocks. Even on Wikipedia it is stated jailbreaking gives one better control over his iPad than rooting an Android device.