NPRM - Notice of proposed rulemaking. A proposed rule lays out how a government agency plans to address a specific problem and requests public comment. After a proposed rule is published in the Federal Register and after public hearings, if the agency holds them, the agency can proceed to a final rule or, if the comments warrant, develop a different rule and re-propose it.
ANPRM - Advance notice of proposed rulemaking. This is used when more information or data is needed to determine whether a rule is needed, what regulation to develop, or to solicit ideas or alternative suggestions for dealing with a specific hazard. An advance notice of proposed rulemaking may be used to alert the affected public about a new regulatory project, or when more information about what form proposed regulations should take, the actual need for a regulation, or other information. The ANPRM may solicit general information or ask the public to respond to specific questions.
SNPRM - Supplemental notice of proposed rulemaking. An SNPRM may be issued if a proposed rule has been substantially changed from the original notice of proposed rulemaking. The supplemental notice advises the public of the revised proposal and provides an opportunity for additional comment.
RFC - Request for Comments. Agencies will use RFC when the want public input on systems, programs and processes outside of the rulemaking process.
RFI - Request for Information. Agencies generally use RFIs when they want public input on how to implement laws passed by congress, whether the agency should issue a new rule, or if there is a need to change an existing rule or policy.