The opinions of the Supreme Court of the United States are published officially in a set of case books, United States Reports.
Opinions are cited by volume number and page number within United States reports, e.g. 383 U.S. 663 refers to an opinion (decision) published in volume 383 of United States Reports, beginning on page 663.
You may see other numbering systems, representing the different reporters (official compilations) that provide access to the document, docket numbers, etc.
U.S. refers to United States Reports, the official reporter for United States Supreme Court cases.
S.Ct. L. Ed is the abbreviation for the Supreme Court Lawyer's Edition.
U.S.L.W. is the abbreviation for the United States Law Week.