The story
Originating from a real-world problem of guarding an art gallery with the minimum number of guards who can observe together the whole gallery.
Etymology from Wiktionary, CC BY-SA 4.0.
art gallery problem
Today it means: A visibility problem in computational geometry, dealing with whether a number of points in a polygon can collectively "see" (by line segments akin to a person's line of sight) the whole interior of the polygon. Full definition →