Lap time
Lap time is the time taken to complete one full circuit, measured from one crossing of the start/finish line to the next.
Also called: lap, best lap
Lap time is the simplest scoreboard in motorsport. Every time you cross the timing line, the clock records a lap. At a track day it is your main feedback, but it is also a blunt one: it tells you that something changed, not what.
Many things besides your driving move lap times: traffic, the temperature of the track, wind, tire wear, fuel load and a yellow flag. That is why experienced drivers look at their best lap and also the spread of their typical laps, and why they break the lap into sectors.
Do not let a lap timer turn an HPDE into a race. The point of the number is learning, not beating the person in the next paddock spot, and pushing for a time beyond your skill is how incidents happen. Look for steady improvement across sessions.
Lap time is the final measure of whether a change worked, provided you compare like with like.