Many empirical studies that examined the government spending concludes that the size and scope of government has grown considerably since the beginning of the twentieth century in most developed countries. If this is the fact, then we must ask and explore the following questions: Why does government grow? What are the main sources of government growth? What are the main reasons of the expansion of government? This introductory paper aims to answer those and other questions regarding government growth. The paper is mostly depend on public choice literature of government growth.