What Tesla Autopilot does, why it's being recalled and how the company plans to fix it

Tesla introduced Autopilot software in October of 2015 with CEO Elon Musk heralding it as a profound experience for people. 

But Musk had an innovation: Autopilot, he said, could change lanes on its own. “It will change people's perception of the future quite drastically,” Musk said while cautioning that drivers still have to pay attention. 

Eight years later, U.S. auto safety regulators pressured Tesla into recalling nearly all the vehicles it has sold in the country because its driver monitoring system is too lax. The fix, with more alerts and limits on where the system can operate, will be done with a software update. 

Here's how Autopilot has evolved over the past eight years and why it's being recalled: