Turns on click-by-click screenshot tracing. While it's on, every button and menu you click gets a screenshot alongside its entry in the event log -- so if something breaks a few clicks later, the next support bundle you build shows exactly what you clicked and what the screen looked like at each step.
It is not video or screen recording -- nothing captures continuously, and nothing is sent anywhere on its own. Screenshots stay on this machine until you build a bundle (or click Start again, which clears them).
When to use it: turn it on right before you reproduce a problem, click through the steps, then immediately build a Support Bundle. Turning it on and leaving it running all day just accumulates screenshots you'll never look at.
Click logging itself (no screenshot) always happens, trace mode or not -- turning trace on only adds the picture.