Unlike open captions, which are permanently burned into the video image, closed captions can typically be toggled on or off by the viewer and are provided as a separate text track. Good captions include not just dialogue but relevant non-speech audio information, like [phone ringing] or [tense music], since that context matters to understanding the video.
WCAG success criterion 1.2.2 requires captions for prerecorded video with audio at Level A, and auto-generated captions, while a useful starting point, frequently contain errors serious enough that they should be reviewed and corrected before publishing, not relied on as-is.