Usually, they give you what they have available at the time. 2 weeks ago I rented a car at the San Francisco airport. They gave me a choice between a Hyundai Sonata and a Chevy Impala.
not always the same car in the advertisement. They often do this to bring you in the shoot you out the door in a beater. You can call and see what models and years of the car they offer. Depends on the area what you might end up with.