Ratings....How do you know?

Once you get 41 more posts you'll see a star beside your username. How do I know my rating and how do I know I'm being rated? Well... My star always changes or its constantly kept at 4 or 5. Anytime I get out of it, a troll and his/her nag friends comes to "put me back in my place" You can check my discussions and responded to, some of my posts are really high in quality.