Who is Jack from The Innocents Abroad and what is their importance?

Jack is the young man who attempts to keep a moment by moment diary of the entire journey. He is convinced that his travel journal will be so detailed and so interesting that he will be able to sell it and make a profit. He writes diligently at first, but less frequently as the days go on. He later gives up the task completely after skipping several days of journal writing. Jack is sent on the excursion by his parents, who hope that he will learn culture and grace enough to not be a constant embarrassment to them.