This indicator marks the start of each trading session around the world, starting with Tokyo at 0am UTC, London at 7am UTC, NY at 12pm and Sydney at 9pm, is non-intrusive (light gray vertical lines) and works with both UTC and exchanges' local time and handles DST / timezone offsets as well.
You can easily see that sometimes it acts as pivot-point especially on high volume.
And last, it is supposed to replace the "Session breaks" option that you can find in "Settings - Appearance" that only displays the end of session for the current exchange.