A 3 dimensional figure
the 3 dimensional shape is a octagon, because their are 8 sides.
A pyramid
If its 2-dimensional then its an octagon, if it is 3-dimensional then it is called an octahedron.
A cube and a cuboid
octahedron
-1
A polyhedron is a 3-dimensional shape whose faces are all polygons.
A triangular pyramid.
edge
A triangular dipyramid.
They are the points where three (or more) planes (or faces of the shape) meet.