Jailbreaking an I device, opens it to more software for it, using cydia, or installer (one Of which apps will be installed as you jail break it) has many, themes, tweaks, and even games. It opens your idevice to many many new things that you cant do on an unjailbroken device. I am even typing this answer on a jailbroken iTouch 4.
Just read up more on it to see of that's what you would like to do.
... nothing
just go to www.freewebs.com/gordonaton
You can get free backgrounds, free apps, and free music by downloading apps
all your current apps will stay the same after jailbreaking.
no, to get a newer jailbreak you have to restore the ipod touch and then update the ipod touch and then download the jailbreak. that is a huge con for jailbreaking.
How to jailbreak my iPod touch
No currently there is no jailbreak available for the ipod touch 2nd gen
You can turn off the iPod Touch if you jailbreak it.
You cannot put themes on an iPod Touch without the jailbreak.
Yes, you can "Undo" a Jailbreak, by going into iTunes and Restoring your iPod Touch, or iPhone.
Yes you have to jailbreak
You get a second app store and more access/customization options/control over your device.