They could be pentahedra in the form of triangular prisms or octahedra in the form of triangular antiprisms.
A triangular prism.
A triangular prism would fit the given description
The figure would be a prism. However, congruent polygons in parallel planes are called bases.
It is a prism. More specifically, "A solid figure that has two bases that are parallel, congruent polygons and with all other faces that are parallelograms." This describes the general prism. Replace "polygons" with "triangles" and you have specified a triangular prism.
Polygon
It is a polygonal prism.
It is a polygonal prism.
Obviously some kind of PRISM.
A prism. A triangular prism has two congruent triangles as bases, rectangular prism, pentagonal prism, etc.
A prism has two parallel and congruent bases in the shape of polygons. Example - a cereal box (is rectangular prism). The top and bottom are rectangles(a polygon). They are the same size and shape (congruent) and also parallel. A cube (think of six sided dice) is a special rectangular prism. Imagine a a box where the top and bottom are triangles (of the shape size and shape). This is called a triangular prism.
Prism!
If, by parellel you mean parallel, the answer is a prism.