Your rating (combined with your opponent's rating) give a way to estimate your performance in a game or series of games. It's based on your previous performance, both in terms of your score and who you played.
Both 65 and 85 would be incredibly bad numbers. The average around here is 1350. The top 5% of players here are easily over 2000.
I wrote a blog post giving a more detailed description of the ratings.
What does this rating represent? What is a solid number. How does a # like 65 compare to a # like 85.