Federal regulations are written by executive agencies to enforce the statutes passed by Congress. They have the force of law, and provide detailed instructions on how agencies intend to enforce laws. In the same manner as federal laws, federal regulations are published in 2 ways and are available in print and electronic form:

The Federal Register [FR]
The chronological version of new regulations, proposed rules, and notices from federal agencies

The Code of Federal Regulations [CFR]
A codified version of regulatory law (arranged by topic) with all obsolete rules removed.

Published by the Office of the Federal Register, National Archives and Records Administration (NARA), the Federal Register is the official daily publication for rules, proposed rules, and notices of Federal agencies and organizations, as well as executive orders and other presidential documents. [U.S. Government Publishing Office]

The Code of Federal Regulations (CFR) annual edition is the codification of the general and permanent rules published in the Federal Register by the departments and agencies of the Federal Government. It is divided into 50 titles that represent broad areas subject to Federal regulation.