This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book focuses on the labor market processes and outcomes of foreign-born persons in the United States, such as unemployment, quit rates, job finding rates, and rates of leaving the labor force. It provides the background on immigration issues, and further detail about the issues. The book introduces a few of the key models of labor turnover and reviews the empirical evidence of the models developed. It develops the estimating equations and the methodology, and defines the explanatory variables. The economic issues can be classified as market and nonmarket issues. Market issues can be further classified into three concerns: the effects of immigrants on the wages and employment of certain groups of native-born workers; the effects of immigrants on the aggregate income and social welfare of the native population; and the experience of immigrants in the labor market.