what is public trustee sale?

Can somebody please recommend me a site/ a book on how public trustee sale work?
I am interested in:

  1. Who can bid?
  2. Can my bid be lower than their asking price?
  3. What are the things to watch for? (additional liens on the property that I’d be responsible for, not clean title, etc?)
    Any info/input would be much appreciated.
    Thanks