I have covered projectors in depth in another article (it is from 2014, so it needs an update as well) so I won’t go into detail with them here.
It is important to remember that they are not much more than a fancy implementation of a light source, an imaging element and a lens. They are best for darker environments, but they tend to be the most economical choice for large scale imagery. It is also easier to blend multiple projectors together more seamlessly.