I created some playlists on iPOD using iTunes.
I put a lot of songs in my playlists, but they do not show up on iPOD. Only the empty playlist appears.
It's not clear (to me) exactly what you've done, but:
the recommended method (by most of us here) is that you create the Playlists in your iTunes Library, add the songs to those Playlists, in your iTunes Library and then (and only then) connect your iPod to your computer so that iTunes can then Sync (synchronise) with the iPod.
In other words, make the changes in your iTunes Library before connecting the iPod to iTunes. Once the changes are made, connecting the iPod to its Library and allowing a Sync to take place does just that - it synchronises (synchronizes in the USA).
If you try to make changes on the iPod, but through iTunes, it can cause all sorts of issues. Furthermore, making changes in iTunes with the iPod connected usually results in the Sync finishing before you do, so some or all of your changes do not get actioned on the iPod - because the Sync has already finished.
Of course, this assumes that you are using Sync to manage your iPod. If you are using Manually Manage instead, it's all much more difficult.