Paradox illusions are generated by objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircases seen, for example, in M.C.
Escher’s Ascending and Descending and Waterfall. The triangle is an illusion dependent on a cognitive misunderstanding that adjacent edges must join. (pic below is Escher’s Ascending and Descending and Waterfall. But not the original (left). The one on the right is the original) also the one below is drawn out, but behind the scenes in real life the water never goes up it just looks like it does.)
Basically they are images that look real but are actually impossible.