The MP4 video format is a high quality video file and the format is compatible on most platforms, including your iPod.
The 3GP format on the other hand is especially useful for mobile phones. Because of its small file-size, it still retains a decent level of quality, and this format can be played back by most mobile phones.
Once you have the videos on your computer, you do not have to be connected to the Internet for watching those. If you wish, you can even burn those videos to a DVD.
Summary!
With this handy tool, you don’t have to be dependant on the internet for watching your youtube videos. Just download all your favorite videos on your computer and watch them at your leisure. You can even burn the downloaded videos to a DVD by using Nero or by using open source tools such as InfraRecorder (free tool).