There’s an important difference between “direct” and “nonstop” flights which you may not have known, Travel and Leisure website noted.

The "direct" concept consists in the fact that the flight number won't be changing even if there were one or more stops, while the "nonstop" flights take you from one airport to another without stopping.

“A direct flight is a carryover from the days when flights between major cities routinely made intermediate stops,” pilot Patrick Smith wrote in Cockpit Confidential.