Projection mapping projects video onto an irregular surface (a building façade, a product, a stage set) with the image pre-warped so it fits the geometry exactly. Done well, the surface appears to change rather than to have something projected on it.
It is the only display technology that can turn an existing physical object into a screen without altering it, which is why it dominates launches, heritage buildings and any venue where a panel cannot be mounted.
The caveat is that it is an event technology wearing a permanent-installation costume. Everything depends on the projector staying in precise alignment with the object; a knock, a thermal shift, or a building settling ruins the mapping, and re-aligning is skilled work. Ambient light is the other constraint: outdoor mapping needs darkness, which caps the usable hours.
Cost is dominated by content, not hardware. Every second is authored for one specific surface and cannot be reused anywhere else, so the asset has no life beyond the installation. Budget it as a production, not as signage.