What's the difference between a Player Library and Windows Library? I am very confused.

Player Library and Windows Library are very different but also related.

Player Library:

• Created and managed by Windows Media Player 12.
• Contains links to media, like music and movie, folders.
• Has 5 Player Libraries: Music, Videos, Pictures, Recorded TV and Other Media
• Linked to default folders: C:\Users\userid\Music, C:\Users\userid\Videos, etc.
• Can link more folders in Player Libraries.
• Cannot create your own new Player Library.

Windows Library:

• Created and managed by Windows system.
• Contains links to any type of document, including music and movie, folders.
• Has 5 default Windows Libraries: Documents, Music, Pictures, Podcasts, and Videos.
• Linked to default folders: C:\Users\userid\Documents, C:\Users\userid\Music, etc.
• Can link more folders in Windows Libraries.
• Can create your own new Windwos Library.

So if you link a music folder in the Windows Library "Music", it will not show up in the Player Library "Music".

You can blame Microsoft for this confusion.