The over-the-air update enables thousands of owners who purchased FSD to use Autopilot's advanced driver-assist features on local, non-highway streets. Elon Musk has been promising this version since 2018 and it's been delayed multiple times. It also adds improvements to the cabin camera's driver monitoring to check for attentiveness, and larger visualizations on the in-car display. Autopilot is still considered Level 2 ("partially automated") by the Society of Automotive Engineers' standards (and by Tesla's lawyers), and requires that drivers keep their hands on the wheel and eyes on the road. Link
