I will give it my best shot! Classes are based on HP (not sure what determines HP baseline), weight and transmission (auto or clutch). The class index is a standard ET set for each class and only comes in play during qualifying, the further you are under the class index the higher you qualify. Class eliminations are a separate race during the event where cars in the same class race each other heads up, no breakout, first to the line wins. Not sure if points are awarded for class eliminations, but a lot of bragging rights are. For regular eliminations racers use a dial in based on their calculation of what they think the car will run. So, once it becomes race day, it is essentially a bracket race with handicap starts and break outs come into play. I hope this helps and didn't offend anyone in the process!