Imagine a movie projector or a slide projector from school.
The image is placed in front of the light and then like a movie projector the image spreads through space.
When it hits a surface it will lay that image against the surface (like a movie screen) and also can distort (like if you projected onto a mountain texture)
There’s a bunch of different names for it, But “Projected Texture” or “Texture Projection” is most common.
See this thread of Paul making a version a few years ago with a nice example
Also, go to the spotlight example I sent, it has helpers and guides to show you what the light is doing.
Open the raw image file to see the baseline image then compare to the 3d scene… see how it gets spread and what all the options do etc