auto finance company

An article in the New York Times in early 2010 noted that: “many car loans have already become significantly more expensive, with rates at auto finance companies rising to 4.72 percent in February from 3.26 percent in December, according to the Federal Reserve.”
a. What is an auto finance company?
b. What advantages might automobile dealers gain from using a finance company, rather than a bank, to finance their customers’ purchases? What advantages might customers gain?