1.) A popular animé and manga with an emphasis on car racing, specifically drift
2.) One of the most popular arcade games all over the world, named, and modeled after the animé/manga.
It allows players to save their car's tuning information on a credit-card-sized magnetic card.
Each new version of the game (currently, there are three) features new cars, new tracks, new conditions, improved physics, and better balancing of the cars.
Check out any book store, and you'll probably find the (somewhat butchered) Tokyopop translation of the manga.
In most video game stores, or any stores selling animé, you should be able to find the animé series.
And the game can be found in any decently large arcade. (Initial D is one of the most expensive arcade machines, ranking up with Bemani