For those of us who don’t regularly follow racing and only watch one or two races a year, all the different flags of Nascar racing can be confusing.
The first flag shown in a race is the green flag, meaning the race has started. Assuming all goes completely according to plan, which rarely, if ever, happens, the next flag shown would be the white flag, which signifies that the race lead has one lap to go in the race and, subsequently, the checkered flag would be shown when the first car to complete all the laps crosses the finish line.
When there are complications in a race, a yellow flag, or caution, may be used; this means all cars must slow down and line up behind the pace car because of an accident or debris on the track. When a red flag is used, cars must stop in a designated area of the track because of hazardous weather conditions. Black flags tell a driver to go to the pit, either because he/she did something wrong or because his/her car is not fit for the road, and are followed by black flags with a diagonal white stripe if a driver ignores the flag, meaning their scores have been suspended. The lesser-seen blue flag with a diagonal yellow stripe tells a car that a faster, lead-lap car is about to overtake them and that they must yield to it.
Finally, perhaps the most confusing of these, is the green-white-checkered finishing sequence. If a caution is shown during the final two laps of the race—i.e. after a white flag is shown—instead of a checkered flag ending the race, a green flag will be shown, and then a white, and finally the checkered flag. This is to ensure that a race does not end under a caution and can happen up to three times if more cautions are given during the final laps.