A classic car (or collectable automobile) that's used as the owner's primary transportation. Contrast with trailer queen. The chances of such a car being driven regularly tend to be in inverse proportion to its value, which makes a lot of sense.
Some drive a really old car every day because they believe that a car is meant to be driven, rather than sit and be admired as a static object. Others take pride in being able to keep their vehicle in good enough condition to be reliable transportation even after so many years. Yet more would rather put all their money into their old car than have a car loan to pay off on something they're not interested in. And for some, space or money don't permit more than one car in the driveway.
An old car used as a daily driver will be in top physical shape, generally, and reasonable cosmetic shape, but no car driven that regularly can be kept in white-glove concours-winning shape. The kind of owner who wants to drive a classic regularly will also tend towards accepting compromises in originality in favor of mechanical reliability and passenger convenience and comfort. The tires will be modern; there will most likely be an updated stereo and speakers, though many will choose models or locations that don't require major surgery to the interior. Changes made under the hood in the interests of better operation will generally be quite acceptable to such an owner, even if they want to leave the car largely original in appearance.
The attitude of other automobile enthusiasts about such a car is normally one of respect that the car is kept in such good condition as to be reliable, mixed with some trepidation (if they don't drive their own cars regularly) about the idea of risking it in rush-hour freeway traffic.