ipod touch 5 - songs that are in itunes via cd, imported to new ipod with red circle with red box and I cannot play these songs. Why?

I just received an ipod touch 5 - I even updated the software on it and have the latest version of iTunes. I had an ipod nano 4. When I synced my music, some of the songs that are in itunes via cd, imported to new ipod with a red circle with a red box inside. I cannot play these songs. Why? And how do I fix this?