Currently Being ModeratedAug 10, 2013 9:04 PM (in response to purplelightning18)
If an iPod is set to automatically sync from a particular iTunes library, when you connect it to that iTunes library, every song on the iPod exists in the iTunes library. Therefore, if you want to play a song on the iPod using iTunes on the computer, you can just play that song from the computer's iTunes library, and not the iPod.
If an iPod is set to load songs manually (by dragging songs to the iPod in iTunes), then the iPod is NOT syncing to a particular iTunes library. The library on the iPod is separate; songs on the iPod may not be in the computer's iTunes library. Therefore, you can play songs stored on the iPod using iTunes on computer.
If your shuffle happens to be 1st or 2nd gen, they work differently from other iPods. They are always associated with only one iTunes library at a time, so you cannot play songs on the shuffle using iTunes on the computer.
I was wondering how I could transfer music from my iPod to my library
You cannot transfer song files from iPod to computer using iTunes (except for songs purchased from the iTunes Store). However, there are third-party methods and utilities that can transfer song files from iPod to computer. If you do a Google search on something like "ipod transfer," you should get some links.