If your new to racing, some of the terms might be confusing or you might not understand them. Here is the start of an appendix for you in no particular order thus far:
Flat track: Typically, oval shaped tracks in varations from 1/4 mile in length to 3/8 mile or more. May also be Round (circle track) or even D-shaped. Flat tracks are almost always a real hard packed, sticky type of clay that gives extreme amounts of hook up.
Hook up: Traction, the amount your wheels and tires spin or slide.
Blue Groove: What happens to a flat track after it has been ran on enough that the rubber from the racers tires actually transfers down to the clay and starts leaving big black places on the track similar to asphalt. Although the clay and the rubber compounds mix and sometimes cause a chemical reaction that makes the rubber streaks look blue in color.
Heat: Although race formats vary from track to track and series to series a heat race is normally a way to eliminate riders and get the total amount to be racing in the Main event to a more managable # that can all be ran on the track at one time. IE, track can only handle 20 racers at one time on the track, 40 racers in one class the heats are used to eliminate and advance riders to a # that can be ran all at one time in "The final/Main event". IE, Heat #1 10 riders advance, 10 riders do not. Heat #2, 10 riders advance, 10 riders do not. The top 10 riders from each heat will go to the main event. In some situations (as discussed below) an LCQ may then be ran with the racers that did not advance from the first and second heats, where the single winner only will advance to the main event. If using heat races to control the amount of racers in a main event is not necessary, it may be similar to a practice, but will normally actually use the starting gate or normal race procedure VS just coming onto the track like you would in a practice. Typically used in MX, flat track, TT.
LCQ (Last Chance qualifier): Similar to a heat race, but in instances where it is necessary only the first place finisher of this race will advance to the main event. Typically used in MX, Flat Track, and TT only when there are more riders in a class then the track can handle at one time for a main event.
Main event: The last race of the event, normally the most important one. Depending on the venue you may be scored exclusively on how you finish in the main event or with a combination the outcome in your heat(s) AND main event.