In real-world speech, there is a natural cadence – slowing down, speeding up, pausing – that cannot be conveyed by the transcript and punctuation alone. The speaker doesn't always pause on every comma or colon, or even on every period. On the other hand they will pause in odd places as they try and grab the right word, or process an idea in mid-flight.
The yellow dots reflect the real-world pauses in speech. Not only does it show you the rhythm ahead of time, we jump to these dots when you tap "rewind" or "fast forward" so you can navigate more easily and naturally.