The major point of this book is that government should stay out of economics for the most part. The book argues that there is an "invisible hand" that will lead to a strong economy if the government will stay out of the way.
At the time when Smith was writing, governments were deeply involved in economies. In particular, governments practiced mercantilism -- a system which strictly restricted trade. Governments believed that regulations like these were the way to increase a nation's wealth.
Smith argued, by contrast, that wealth increased when businesses were free to do as they wished -- when trade was unimpeded, for example.
Smith's name is connected with the idea of laissez-faire capitalism because of the message of this book -- that government should stay out of the economy.