Use cue marks or segment marks to mark frames of interest on a clip. You can then quickly go to the marked frames. These marks are for reference purposes only; they do not affect the clip and are not used in any editing operations. You can add a mark to all tracks (cue mark) or to a single track or version (segment mark) on the timeline. Segment marks move on the timeline as you trim, slip, or slide a clip whereas cue marks stay at the same position on the timeline.
You can also add In and Out marks on timeline clips, as you can in the player.