Bit of a longwinded way of saying modular assembly. The Yanks were doing it with Liberty ships and then Victory ships in 1941. Pre-fabricated completed sections of the ship were made at remote workshops, trucked to the shipyard and welded in place in one go, instead of being made from the ground up on site as they went. They could build a ship in 42 days. Submarines were built the same way when I worked in the boatyard in the 1990s. Made in sections with all internals completed, then the sections were welded together like so many lengths of very large pipe.
It's a good idea and somewhat innovative in the car industry. But there is the usual cloud of Musk hype around it. Grain of salt may be required.
Interesting that even with all the automation and thus hardly any labor costs (comparatively) they are still proposing the new Tesla plant for Mexico where labour is cheaper than the USA. Will they never be happy until they get their cars made for free?