loved

I was looking at my music library in the Apple Music desktop app, and I noticed some songs had red heart icons next to them, indicating that I had "loved" those songs, of course. There were also some songs that had just the red outline of a heart next to them. What does this indicate?

Curious if anyone has noticed Apple Music recommendations improve as a result of "loving" tracks. Up until recently, I never "loved" tracks, but Apple's recommendations haven't seemed to improve either. Does anyone use this functionality and if so, does it seem to make a difference?