First the foundation is completed. Then they install steel rebar and put the aluminium forms on each side of the wall. Then they install aluminium forms on the ceilings. After pouring the concrete, they let it cure and repeat. Aluminium formwork has the benefit of being reusable and can hold up to over 1,000 applications. The forms install very fast. However metal forms are expensive and because they are less flexible, their use can be limited to straightforward sections of condominiums. Wood formwork is still commonly used by builders where labour rates are lower than the cost to procure metal forms, or the builder is just entering into the condo market. In this case, wood studs hold together sheets of plywood or moisture-resistant particle board. Wood can only be recycled for a few applications before it loses its strength. Wood is often used to form complicated sections of a building even when aluminium forms are being used. This is because wood is the easiest to shape and work with.
Here is useful animation to show you how they create each level of a concrete high-rise building using aluminium forms. This is a basic building and does not cover all aspects of modern design.