Do you mean that your iPad has been jailbroken or just your son's iPod Touch?
Jailbreaking is a process that allows iPad, iPhone and iPod Touch users to run third-party unsigned code on their devices by unlocking the operating system and allowing the user root access. Once jailbroken, iPhone users are able to download many extensions and themes previously unavailable through the App Store via unofficial installers such as Cydia.
for more information, see here:
http://en.wikipedia.org/wiki/IOS_jailbreaking
It is pretty much a customization tool which enables more freedom with your device, but it may void your Apple 12 month warranty as it does not comply with their software regulations and policies. Just make sure you restore to factory settings and it should be gone.
Some features are illegal, such as installing apps which are available in the App Store for free via a separate source through Cydia.
You can jailbreak a device simply by downloading a package, connecting your device and hitting 'Jailbreak' which would install whatever is in the description of the package.
Back Up your device by right clicking your connected device in the left hand pane in iTunes and clicking Back Up.
Then you can restore. No information should be lost, except Cydia and all things related to it.
Kids are catching on these days!