Flexible polyhedra

Can a polyhedron be curved? Perhaps this is some kind of mistake? Or maybe this is not a polyhedron? It turns out that there are flexible polyhedra.

Alexander Gaifullin says that there are other types of polyhedra - flexible polyhedra.

To illustrate the usual polyhedron, Alexander uses the icosahedron assembled from our set "Magic Edges"!

Used materials video project "Postnauka" (http://postnauka.ru/).