What is the BEST description of a change proposal?

Describing any RFC submitted to change management is too broad and does not reflect the specific significance threshold or justification purpose that defines a change proposal.

An authorized change submitted to release and deployment describes a change that has already been approved and is moving through the pipeline, not the initial justification document.

An RFC that must be implemented as soon as possible describes an emergency change, which has its own separate process and expedited authorization path.

A change proposal is specifically used for significant changes that involve high cost or risk, such as major projects or strategic initiatives, and is submitted to change management before detailed service design begins. It allows the change authority to evaluate feasibility, cost, and risk before committing resources. This distinguishes it from a routine RFC, which covers lower-impact changes.