Here are fine houses and shops full of goods, but yonder is poverty and slums. It doesn't make any sense unless we understand the basic principles of economics. Once we have this understanding, the economy becomes clear - we see the cat instead of a jumble. We then know the cause of poverty and its remedy. But since most folks don't see the cat, social policy just treats the symptoms without applying the remedies that would eliminate the problem.
Land includes all natural resources and opportunities.
Labour is all human exertion in the production of wealth. The owners of land get rent, workers get wages, and the owners of capital goods get a capital return. Picture an unpopulated island where we're going to produce one good, corn, and there are ten grades of land. We'll ignore capital goods at first. The first settlers go the best land.