Review Mode vs Work Mode

Once your subtitles are done, you can review your work by switching to Review Mode.

Review Mode lets you play the video whilst showing you the timed subtitles, whereas Work Mode only shows you the subtitle you have selected in your subtitling area.
Basically, Review - for previewing, Work - for timecode editing and creating subtitles from scratch.
Review mode will update the visible subtitles on the video according to the current video time and will also automatically select the same subtitle row on the table.
Work mode will show the currently selected subtitle on the video and will not change the selected subtitle when the current time changes.