Jailbreaking was created to break free of Apple's restrictions. They make sure you cant install third party applications, only the ones that they approve. Jailbreaking allows you to install other applications that aren't in the App Store. For example, an installable third-party app called Winterboard allows you to customize every aspect of your iPod. From status bar themes, to app icons, to lockscreen, to complete GUI overhauls.
Jailbreaking is also possible on Android devices, through the more commonly known term of "rooting" your phone. Similar to jailbreaking an iDevice, rooting allows you to break free of restrictions and customize almost anything and everything about your device, similar to Winterboard on iOS, as well as give you "root" permissions for apps which allows you to have even more functionality.
obviously, as you cannot get them w/o jailbreaking
Yes, jailbreaking does void the warranty.
"Jailbreaking" is another word hacking. Therefore you void your warranty but you get cydia, a jailbreaking software. Jailbreaking does have it advantages and Disadvantages. But if you want to send it to apple to repair it you have to restore it to factory settings to get back your warranty.
Yes; not jailbreaking it. If you mean a way to do the same thing as jailbreaking without actually doing so, there is no current way to do so.
Jailbreaking a phone is partially legal and partially illegal. I have a post regarding this http://www.techlucid.com/2013/11/is-jailbreaking-illegal-or-not/
It is impossible to get an installer on an iPod Touch without jailbreaking.
It is up to you. No matter what you have on your ipod will become messed up when Jailbreaking...
By jailbreaking it.
No
no, it is not illegal
no
As of today (November 24th, 2010), jailbreaking an iPod Touch is not illegal. Is it 100% safe? No.