If you plan to use concrete for building, you can either have it made onsite or prepared beforehand in a dedicated factory. The latter is called precast concrete. This has numerous advantages over the other former including lower formwork cost, greater site safety, and higher material quality.
A piece of precast formwork can be used multiple times to create hundreds or even thousands of similarly shaped concrete. The cost per unit is significantly decreased as a result of scalability. And since the final product was cured inside a controlled environment, it exhibits characteristics that are closer to the ideal.
Site safety is also increased because the pouring is always done on the ground where there is little risk of spilling. It tends to get trickier to go the traditional route as the building gets taller. Going precast is the way to go.