The United States Court system has three tiers:
Opinions of the United States Supreme Court are published in three different reporter series: the government issued, official reporter, United States Reports, and two unofficial, commercial reporters: West's Supreme Court Reporter and United States Reports: Lawyer's Edition.
Opinions of the United States Courts of Appeals are published in West's Federal Reporter series, and opinions of the United States District Courts are published in West's Federal Supplement.
More recent unpublished or yet-to-be-published opinions from the US appellate and district courts can be found on the websites for those courts.
Specialized courts often have their own reporter series. Examples of specialized reporters include West's Bankruptcy Reporter for bankruptcy courts and West's Military Justice Reporter for cases from U.S. Court of Appeals for the Armed Forces and military courts of criminal appeals.
The official reporter of the United States Tax Courts, published by the U.S. government, is the Reports of the U.S. Tax Court (T.C). Another source for federal tax cases is U.S. Tax Cases, published by CCH, which includes federal tax cases from the district and appellate courts.