Congress has the power to pass legislation but usually leaves the implementation and the enforcement of that legislation to the federal agencies that make up the executive branch. Regulations (also referred to as "rules") are legally binding and can be enforced as statutes.
Like their statutory counterparts, regulations are published by the federal government in two basic formats: chronological and subject matter. The Federal Register publishes the regulations chronologically; the Code of Federal Regulations (CFR) publishes the regulations by subject matter.
The Federal Register (FR) is the official vehicle for making the regulations and legal notices issued by federal agencies and departments available to the public. These include federal agency documents, such as regulations (proposed, temporary, amended and final) having general applicability and legal effect, documents required to be published by act of Congress, federal agency documents of public interest, meeting notices, and Presidential proclamations and executive orders.
The Code of Federal Regulations (CFR) is the codified form of the regulations. Codification is the process by which the regulations are arranged by subject matter. The complete set of the CFR contains 50 titles. For a list of coverage by title, see the Legal Information Institute of Cornell University. Note that the titles of the CFR do not always match the titles of the US Code.