Short answer - It is a beauty pageant for chickens. You take your best chickens to compete with others that have brought their best chickens and the judge chooses the winners.Just a quick question--
What does a chicken show actually consist of?
If you are familiar with other animal shows, it is a similar concept. Lots of work goes into the conditioning and preparation. You can't just pluck one out of the barn and take it to the show the next day. There are tons of very good information at this website and this thread. Just read, read, read if you are interested in showing.