SMPTE timecode
The HH:MM:SS:FF address of an exact frame: the standard way to point at a moment.
SMPTE timecode identifies a single frame as hours, minutes, seconds and frames: 00:01:23:14 is one minute, twenty-three seconds and fourteen frames in. The frame field counts up to the project's frame rate and then rolls the second over.
It exists so that two people looking at the same cut can refer to precisely the same instant. "Around the middle bit" costs an editor ten minutes of scrubbing. A timecode costs them nothing.
For review purposes you rarely need frame accuracy (01:23 is usually enough), but the discipline of quoting a time at all is the single biggest improvement most feedback can make. Every professional review tool, including Acumin's Delivery Rooms, anchors comments to a timecode for exactly this reason.
Where this comes up
How to read and write HH:MM:SS:FF, why "around the middle bit" costs an editor ten minutes, and the note format that gets acted on first time.
Notes against the brief, at the right stage, from one voice. The three rules that turn a review round from an argument into a version.