From the Introduction: "This report provides a broad overview of U.S. immigration policy. The first section addresses policies governing how foreign nationals enter the United States to either reside permanently or stay temporarily. Related topics within this section include visa issuance and security, forms of quasi-legal status, and naturalization. The second section discusses enforcement policies both for excluding foreign nationals from admission into the United States, as well as for detaining and removing those who enter the country unlawfully or who enter lawfully but subsequently commit crimes that make them deportable. The section also covers worksite enforcement and immigration fraud. The third section of this report addresses policies for unauthorized aliens residing in the United States. While intended to be comprehensive, this primer may omit some immigration-related topics. For example, it generally does not discuss policy issues or congressional concerns about specific immigration-related policies and programs."
CRS Report for Congress, R45020
Congressional Research Service: https://crsreports.congress.gov/