This rating is only use under two circumstances:
Either I don’t like the track, and I will delete it from my library (for obvious reasons, I only end up with this when I am rating from my iPod), or I consider it to be “filler.” A filler track is when an artists has a track of random sounds, or sometimes spoken words, that can not be considered a song by its own merit, but an album would be incomplete without it. An example of artists who do this are Nine Inch Nails, and Tool.
This is a rating that I use for a track that I am not particularly fond of, by an artist that I like well enough that I wouldn’t want an incomplete album, such as in the above example.
This is a neutral rating. When I am judging a track for ratings purposes, I start every track as three stars mentally. Then, as I listen, I will either go up, or down from there. These are tracks that I would not mind listening to, if they were to appear in a playlist that I have set to randomly generate.
One notch above three stars, four stars is approaching “favorite” status. This is a song that I may be likely to choose to play, rather than just listen to it at random.
These are my favorites. In a playlist of all five star songs, there are no songs that I would get tired of hearing, with the playlist on repeat.