A shape created by stacking congruent polygons could be called an “extrusion” of that polygon in 3 dimensions. A “triangular prism” has a triangular base. If you stack squares, you'll have a cube. If you stack octagons, you'll have an octagon prism.

What polygons are congruent?

Definition: Polygons are congruent when they have the same number of sides, and all corresponding sides and interior angles are congruent. The polygons will have the same shape and size, but one may be a rotated, or be the mirror image of the other.

Can two congruent polygons have corresponding sides with different lengths?

In order to be congruent, corresponding sides must be the same length. The regular hexagon has all side lengths with the same measure. The irregular hexagon does not have sides that are the same length. The answer is no, the two hexagons are not congruent as their corresponding sides are not all the same measure.