How come I can put song to my ipod?

Hey everybody..I have a big problem with my ipod....
I can put song to the itues but not the ipod.
When I put in the USB cable and usually it supposed be the itunes will show it is connected
with the ipod right? But now I have no idea of why it is not working.
It can be charged but just nothing happen on the itunes and I cant put new
songs in.
Anyone could answer my questions please????
Thanks a lot
I am gonna give 20 points for that pls