Determination of ad position

How does Google AdWords work? Ad position

Short Extract : of their ad by offering to pay more money, improving your ad's Quality Score is often a better approach. Why? Better quality ads generate more business and save money. Optimizing for Google's Quality Score can help you, because the way Google calculates ad quality is generally in the end-user's (e.g. your customer's) best interest. Better quality ads are probably going to be clicked more often, result in better qualified leads, ...