Final rule
The binding version of a regulation, published after the comment period, with an effective date and the agency's response to comments.
A final rule is the enforceable one. It appears in the Federal Register after the agency has read the comments on its proposal, and it carries two things the proposal did not: an effective date, and a preamble explaining what the agency did with the objections it received.
The preamble is usually the most useful part of the document and the part least often read. It is where an agency states why it rejected an alternative, which is both the substance of the decision and the ground on which the rule can later be challenged in court.
An interim final rule is a variation worth knowing: it takes effect immediately, with comments collected afterwards. Agencies use it when they claim good cause for skipping the usual sequence, and the claim itself is frequently the newsworthy part. The requirement then lands in the Code of Federal Regulations.
What the federal government did, once a day.
One email each weekday: the rules, filings, votes and Fed decisions that actually changed something, each one linked to the document it came from.