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I'm pretty sure you're trolling.

But if you're not...

Cydia is not a jailbreak. Cydia is the app that the jailbreak installs on your device.

Cydia works like the AppStore, except it contains non-Apple Approved apps.

Either use greenpois0n or limera1n to jailbreak iOS 4.1. It's just down to personal choice to which one you use, really. They both use the same exploit.

If you have an iPod touch 2G MC model, use greenpois0n.
 
i don't know which one many people use to jailbreak their ipod touch and have no troubles with it? what Jailbreak should I use??

A jailbreak doesn't do much of anything to the software running on the iPod Touch. It's still an iPod running the firmware Apple wrote for it. All it does is tweak a couple files to remove the restrictions Apple artificially places on the device, such as the inability to run programs that aren't signed with Apple's special key.

Cydia is an alternative App Store. All it does is let you install other programs. Cydia, like the programs inside it, can't be installed unless you jailbreak your iPod but it has nothing to do with the jailbreak itself. Cydia and the programs in it are written just like ever other iOS program, but they aren't published to Apple's App Store. The programs you get from Cydia may crash or have bugs, but then so might the programs in the App Store.
 
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