A docket is a file of documents associated with a particular rulemaking or adjudicatory action. When a rulemaking begins, the agency will open a docket for the rule and give it an identification number. The docket will generally include all relevant public information related to a rulemaking including Federal Register postings, scientific documents used in the decision-making process, agency meeting minutes on the rulemaking, and any public comments filed on the rule.
Each agency sets up its docket system differently and there is no consistency among agencies. Some dockets are available online, but online dockets may not be complete or regularly updated, and it may not be possible to view dockets after the rule has been promulgated. Some departments have a central docket, and other set up dockets by agency. For instance, the Department of Transportation has a central docket system that includes dockets for NHTSA, FAA, etc, whereas HHS and DOL do not have central docket systems. To find the docket for an FDA rulemaking, you have to go to the FDA docket system.
Most agencies' dockets are supposed to be eliminated when all federal agencies migrate this docket information to the federal government's central docket management system by the end of 2007.
When contacting an agency about a rulemaking, always include the associated docket number to ensure that the document is included.