From the Windows Help and Support system: “What is a Library”
“Libraries are where you go to manage your documents, music, pictures, and other files. You can browse your files the same way you would in a folder, or you can view your files arranged by properties like date, type, and author.
In some ways, a library is similar to a folder. For example, when you open a library, you'll see one or more files. However, unlike a folder, a library gathers files that are stored in several locations. This is a subtle, but important, difference. Libraries don't actually store your items. They monitor folders that contain your items, and let you access and arrange the items in different ways. For instance, if you have music files in folders on your hard disk and on an external drive, you can access all of your music files at once using the Music library”.
From the Windows Help and Support. Click Start, Help and Support, In the Search Box type “Libraries” and press enter or click on the search Icon. Click on each section to read it
From the Internet. In the Google search enter “Libraries in Windows” or a term similar to that such as “Libraries in Windows 7” and press enter or click on the Search Icon.
Click on the links to go to the appropriate web page.
If you want to see links to only Videos about then click on the word “Video” at the top of the Google search results or you may have Click on “More” then “Videos”
A brief introduction
http://www.youtube.com/watch?v=GRupayg9uDY
A slightly more detail explanation with how to get more help on them.
http://www.youtube.com/watch?v=jKD7v8BQtfU
This one goes in to slightly more detail again