1 - A female so hot that you would go around and brag to all your friends that you had sex with her. Exceptions are celebrities or other news worthy people. They may be a 2 or a 3, but due to celebrity factors you may brag. As a warning this may not be advisable though. Calling Roseanne Barr a 1 could get you crucified.
2 - A decent looking female that you would have sex with. You wouldn't go around bragging about having sex with her, but when confronted you would admit to the encounter.
3 - A horrible looking female (so you assume). You would still have sex with her, under the right circumstances, but you would never tell a soul. This the type of information you would take to your grave.
"How would you rateher that new secratary?"
"You heard of that new rateher system?"