Laws are enacted by a legislative body (in this case the US Congress) to govern. After a statute is passed by the legislature, it is published in three forms:
Slip laws: individual pamphlets containing the text of a law as passed
Session laws: annual compilations of laws passed in a legislative session
Codes: compilations of the laws in effect, organized by subject
For a more comprehensive overview of the process, check out this resource from the library of congress:
Regulations are statements issued by federal agencies that have the weight and impact of a law. Congress passes laws, but it falls to the agencies to carry out the tasks laws authorize them to perform. The rulemaking process creates these regulations. The best part about regulations is that you can offer comment! On regulations.gov, you can read proposed new regulations and proposed changes and weigh in on them.