Docket
The numbered file that holds everything submitted in one rulemaking or one court case, and the public record a decision has to answer to.
A docket is the file an agency or a court keeps for a single matter. In rulemaking it collects the proposal, the comments filed against it, the studies the agency relied on, and eventually the final rule; in litigation it holds every motion, brief and order in a case, numbered in the order they arrived.
The number is the useful part. A docket identifier is stable, quotable and searchable, so it is the difference between a claim about what an agency proposed and a pointer to the proposal itself. It is also how two documents published months apart are proven to belong to the same decision, which is what makes an agency's reversal visible.
Dockets matter to a reader because they are where the argument actually happens. An agency must respond to significant comments, so the objections filed in a docket frequently predict which parts of a rule will be rewritten, delayed, or struck down when somebody sues. Coverage that reads only the finished rule misses the part that explains it.
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.