What do the letters on American Idol Golden Tickets mean?

American idol
Waterfall asked:

Went to American Idol auditions today and am curious about what the markings on the Golden Tickets they give to each constant mean. They are N, K, or star. Everyone gets either an N or a K and just a few people get stars (usually Ks). I’m thinking that the N means bad the K means good and the star means a featured story– but I’m not sure… please someone tell me!