The height and size of a building under construction can make concreting it difficult without the proper equipment.
A concrete pump mast is the tower that holds the placing boom, which is a crane that pumps concrete into places like slabs, cores, RC frames, etc.
Pipes go from a static pump on the ground, up to the boom head.
The mast gets delivered on a lorry, then gets stood up on end (an end lift), then placed into position.