Finish line usually refers to racing games and often is an official line drawn on the ground, that all racers cross at the end of a race. However, the finish line of a race can really be almost anything; the edge of the grass, the line of a concrete sidewalk, a handy stick, or the edge of a building. Or even, “I'll race you to the lamp post”. It doesn't really matter, as long as all racers agree ahead of time.