Why is my music not appearing on my iPhone?

I have my new iPhone 16 plugged into my PC. I have transferred music to the phone. On the phone the music is not showing up. But looking at the music on my phone in iTunes it shows that the music is on the phone. How can iTunes think the music is there, but I can't see it on my phone? iTunes shows there are 3846 songs on the phone. When I go to the settings on the phone General/About it shows there are 2963 songs. How can they be showing different numbers? Where are the missing songs and how do I get them to show up on the phone?

Thanks

[Re-Titled by Moderator]