Civilization VI is going to bring some changes to the way the game is played compared to Civilization V. Cities and improvements will now take up multiple tiles. And to create improvements, workers have been replaced by builders.
A new video from Firaxis shows off some of the mechanics behind the new unit, including the instanteous creation of an improvement instead of having to wait numerous turns for completion. While this may a welcome change those of us who impatiently wait for upgrades, the drawback is that builders will only build three improvements before they disband. The video mentions "most builders," which means it is possible that some builders may have more charges, either via promotion or as a perk of a particular Civ.
If you are a veteran of the game, these videos are pretty informative about what you can expect when the game hits on October 21.