Google Play Music - Question or Observation

[yeah yeah]

I might have missed something, but....
Been using Google Play Music since it was released. I have a lot of songs in My Library and saved offline onto my device. I usually just hit "Shuffle My Library" for songs that's located on my device, but I'm noticing a lot of songs that I never heard before, not in my library, and definitely not saved offline to my device. How do these songs get there? When I try to search for them, they don't show on my device or in my library. Does Google automatically throw songs in there that I might like?

 

[y2whisper]

when it was released there were a bunch of free songs that we got access to. I forget the steps that were used to get them but if you go to play music on your computer there is a section on the left for free and purchased. See if those are the same songs.

 

[yeah yeah]

Nope. The only thing on there is an album I paid for. When I was driving to work today, hit shuffle my library (on device), and at least 5-10 songs popped up that I know aren't in My Library, and definitely not saved to my device. Still at a loss. I notice these mystery songs are continuing to grow. The other day, I was working out, maybe listened to 30 songs, 20 songs would account for these mystery songs that aren't in my library or saved to my device. I don't like to stream music while I'm at the gym, because certain areas of the gym have weak signal, and I can't stand the buffering...so I only listen to music saved to my phone.