iTunes libraries offer you the chance to sort your music by genre, mood, season or era. Libraries make accessing and searching for your music much easier. You can file holiday music in a separate library, so that it is not included on your regular rotation of songs.
I am sometimes asked , how do I create a new Itunes library and this can be so:

• Your music library is out of control with multiples and you cant be bothered sorting them out
• You want to file ceratin music catagories in sepearte in  libraries

Whatever your reason it is fairly easy.

When you open iTunes just hold down the shift key and a dialogue box will appear.

Click on "Create Library"
You can now begin putting music in your library.

If you want to share the music in your current library with your new library you should click "Copy Files to Itunes Music Folder.

This stops you from erasing the song from the original library.

How do you look for shared libaries ?

On iTunes open edit and select preferences

Look for shared libraries by clicking "Edit," then "Preferences." Then click "Sharing" and check "Look for Shared Libraries."