At the federal level, bills are introduced in Congress and those bills may become enacted laws. Laws are published in Statutes at Large and then later organized by subject into the U.S. Code. The official U.S. Code is published once every six years. Examples of commercial services that provide access to the U.S. Code with case annotations and other features are U.S.C.A. (Westlaw) and U.S.C.S. (Lexis+). A free, unofficial and unannotated online version is available from the Office of the Law Revision Counsel, which is in charge of compiling the code.
At the state level, bills are introduced in the General Assembly. If they are enacted into law, they are published in the Laws of Pennsylvania and then in the statutory code. Pennsylvania has a somewhat complicated system whereby only some areas of law have been codified, so you must check to see if your statute is part of the Pennsylvania Consolidated Statutes or the Pennsylvania Statutes.
Purdon's is an unofficial commercial service that provides annotations and other features for Pennsylvania statutes. An unannotated version is available free online.
Office of the Law Revision Counsel (online version is unofficial, but this agency compiles the official code) (FAQ | Search Tips)
United States Statutes and the United States Code: Historical Outlines, Notes, Lists, Tables, and Sources - A Federal Research Guide, 2019 (Law Librarians' Society of Washington, D.C.)
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