You must think I'm joking about this. You've never heard of Formula 3 or GP2. These are as foreign to you as F1 itself. It is important, however, to make a note of these series, since they are related to F1. In general, these are stepping stone series for drivers who are trying to climb their way up to the highest level - Formula 1.
F3 and GP2 are among the many feeder series in Europe where drivers drive cars that look similar to F1 cars and similar to IndyCars and Champ Cars. But they are much slower and much, much less sophisticated. They do teach the drivers how to prepare themselves for the highest level of what is known as "single-seat, open-wheel racing," however.
Single-seat, open wheel racing is the formula of racing that all of the above series belong to - all except NASCAR, which is not single-seat open-wheel racing. In NASCAR, the wheels are covered, and the driver is covered and not hanging outside the cockpit like an F1 driver.