Most people just call it The Wealth of Nations, but the full title of Adam Smith's book is An Inquiry into the Nature and Causes of the Wealth of Nations. That's because Smith really wants to lay out for people why some countries are wealthier than others.
In his mind, the reason you see more progress in some countries is because they engage in free trade and lots of competition. Countries that lag behind are the ones where the governments try to control the markets and discourage competition. The strange thing is that most of the world was completely wrong before Smith wrote this book. That's why he gave the thing such a plain title. He was writing about something that most people took for granted. Little did these readers know that they were about to have their minds blown by Smith's economic theories.