Since it a shape with 6 faces it is a type of hexahedron.
Essentially, the figure is a cuboid with two of its adjacent vertices brought together. I will try to describe it in a bit more detal:
Start with a cuboid. Take the top-right-front vertex move it to the bottom-right front vertex. Move all the other edges as you go. When you finally get to the bottom you will have the required shape.
octagon
It is a triangular prism that has 6 vertices, 9 edges and 5 faces.
Since it has 9 faces it is a nonahedron. Not sure how many of the thousands of nonahedrons have 6 vertices.
That 3D shape is called triangular pyramid.
tetrahedron
A triangular prism.
Pentagonal Pyramid
the triangular pyramid
Triangular prism
It is a cuboid
A Triangular based Pyramid has 4 vertices, 6 edges and 4 faces.
It is an octahedron that is a 3D shape with 8 faces