What is this build-in-a-factory, assemble-on-site approach called?

Modular, or prefabricated, construction is the name for this build-in-a-factory, assemble-on-site approach, where entire finished rooms, complete with wiring, plumbing, and interior fittings, are manufactured in a controlled factory setting and then transported to the construction site to be stacked together like building blocks, dramatically speeding up the overall construction timeline.

Freehand bricklaying describes the traditional, labor-intensive method of stacking individual bricks by hand on site, essentially the opposite approach in terms of speed and factory-based precision. Slipform paving is a technique for continuously pouring concrete into a moving mold, mainly used for roads, curbs, and similar long linear structures rather than stacking prefabricated rooms.

Because factory conditions avoid weather delays and allow parallel work on multiple units at once, modular construction can achieve astonishing speed, with one 57-story tower in China reportedly assembled from prefabricated modules in just 19 days.