USCIS stands for United States Citizenship and Immigration Services — the American government office that handles the paperwork of coming to and staying in the country. It processes green cards, work permits, visa petitions filed from inside the US, and the citizenship application and test at the end of the road. Most people say the letters one by one, "you-ess-see-eye-ess", though some in the field say "you-siss". It is dry, official language: it lives on forms, on receipt notices, in phrases like "USCIS approved my I-130" or "still waiting on USCIS". Keep it apart from two neighbours it is often confused with. USCIS handles applications and paperwork. ICE does enforcement inside the country. CBP is at the border and airport — the officer who stamps your passport is CBP, not USCIS. If you or a family member ever deal with American immigration, that three-way split saves a lot of wasted phone calls. Before 2003 the same work was done by an agency called the INS, so older books and older relatives may use that name.