Why are my iTunes songs grayed out and how do I fix it?

What I wanted to do is Hide a Playlist (and the songs in it). It's a Christmas playlist, so I only need/want to hear it around that season. I tried a couple of different things, and put myself in a situation I'm not sure how to fix, and then do what I want.

The playlist is still there, but all the songs are grayed out, with a downward pointing arrow, asking me to download the song?

How do I/Should I restore them to the regular black (dowloaded?) version. Then how can I hide the playlist/songs (so they are not visible/Playable) to restore it later in the season?

*Half I had Purchased on iTunes, others I had the CD and put them on iTunes. Can you hide those the same way, or it only works with purchased music

[Re-Titled by Moderator]