The 15 Cabinet departments are the largest executive departments. Each is led by a Secretary or, for the Department of Justice, the Attorney General. Those officials are nominated by the President and confirmed by the Senate. Cabinet departments often contain many bureaus and offices, so a visitor looking for a public service may need the department first and the specific bureau second.

Independent agencies and commissions are created by Congress to carry out specialized duties. Some operate public services, like the Postal Service. Others regulate markets, enforce civil-rights or workplace laws, insure deposits, run archives, or publish data. Their independence varies. Some leaders serve fixed terms. Some boards are bipartisan by statute. Some still answer closely to presidential direction.

Many familiar federal offices are not standalone departments. They are bureaus, administrations, services, or operating components inside a parent department. The FBI sits inside the Department of Justice is a federal department, agency, office, or public institution connected to the administration of federal law, services, records, or policy.">Department of Justice. The IRS sits inside Treasury. TSA and FEMA sit inside Homeland Security. CDC, FDA, NIH, and CMS sit inside Health and Human Services. The parent department matters because it affects budgets, leadership, oversight, and official source trails.

Start with the service or record you need, not with an agency name you half-remember. If you need a benefit, form, license, report, complaint channel, public dataset, grant, Act, the federal law that lets the public request many agency records.">FOIA office, or local office, open the relevant agency profile and use the official links there. When a topic appears political, check the Executive Branch page; when it appears administrative, check this directory; when it involves a proposed or final regulation, check the rulemaking pages.