Federal statutes enacted by Congress and signed by the President (or passed over the President's veto) are compiled into the United States Code (U.S.C.). The U.S. Code, organized by topics into a series of titles, numbered from 1 (General Provisions) through 50 (War and National Defense) , contains nearly all statutes of general effect at the time of its compilation. For more recent enactments one must turn to the uncompiled statutes in the form passed by Congress.
In sum, to be sure of an up-to-date picture of the statutes dealing with a topic one must consult both a version of the U.S. Code and also determine whether there have been pertinent amendments or additions to the law since its date of compilation.
Some commercially published editions of the U.S. Code include useful editorial notes detailing the changes over time that lie behind current provisions and summarizing court decisions and regulations interpretting them. References to U.S.C.A. or U.S.C.S. rather than U.S.C. alone indicate the use of such an edition.
When a judicial opinion or other legal document refers to a particular statutory provision, it will normally cite to its location in the U.S. Code. See, for example, Things Remembered, Inc. v. Petrarca dealing with a statute addressing jurisdiction by Federal and state courts in situations of bankruptcy. The decision focuses on the language of "28 U.S.C. § 1452(a)" -- which is subsection a, of section 1452, of title 28 of the U.S. Code.