Hi Andre, and welcome to AF
For questions about root and ROMs for the GNote the place to visit is
Galaxy Note - All Things Root - Android Forums. Rooting is device-specific, and that's where the experts on that device will hang out.
Rooting basically means gaining superuser (administrator in Windows terminology) access to your phone. It allows you more control over the system, and the option of changing things that you previously could not (e.g. removing system applications, though on some devices additional steps are needed for that). The procedure also gives you the capability of replacing your system software with a custom version, aka "changing ROMs".
De-odexing is a matter of how the components that make up an app are arranged. The main motivation is really that it makes theming easier. Many or most custom ROMs are deodexed, so rooting then changing to one of these is probably the simplest way.
As I say, rooting is device specific, as are the ROMs, so the place to go is your device's All Things Root subforum. The people there will be able to help you out
