Professional, experienced, thorough, and driven to find the talent you need.
A casting director is someone with an eye for talent who is hired by a production company or an advertising agency to find the talent they need, thus saving the production company or ad agency time and ensuring that they are considering the best talent available. Casting directors go to talent agencies and other resources to find the best talent on a job per job basis. They also stay knowledgeable of the talent pool by occasionally having general calls and individual interviews with actors, teaching classes, and attending local shows.
As a general rule, casting directors should NOT take any money from actors unless they are teaching classes. They generally have NO professional association with a talent agency. They mostly work like independent contractors whose sole allegiance and bias is to the production company or ad agency that hired them.