How come my music on my iPod in itunes is highlighted gray? It's like locked and I can't add music to it.

That's by default. iPods by default work by syncing. That means whatever you have in your library will be on your iPod.





If you want to edit it manually, then click on your iPod in iTunes, at the bottom of the main screen, it should have an option for ';Manage Music Manually';





Check that and then it will be all black.