The entrace to a pyramid faces the North.
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A hexahedron or a triangular dipyramid. This is the shape formed by two triangular pyramids (tetrahedrons) stuck together along one triangular face.
This sounds like you are talking about a pyramid. Pyramids in Geometry are not restricted to the square pyramids you may be used to seeing in pictures of from Egypt. Pyramids are named after the type of polygon that make up their base. In Egypt, since the bases of those pyramids are squares, they are known as square pyramids. If you had a pyramid with a pentagon for a base, then it would be a pentagonal pyramid. Pyramids always have triangles for sides that meet at a common point at the top which is known as the apex.
Both pyramids and prisms are three dimensional. Both of them have polygon faces. Another thing common about pyramids and prisms is that they have a base and faces.
None, really. Except that when a solid has faces of two kinds and there are only one or two faces of a particular shape then the solid is conventionally viewed with that face at the bottom (and top) and the bottom face is called the base. Common examples are pyramids or prisms which may have bases that are triangular, quadrilateral, pentagon etc. Or cones and cylynders whose bases may be circles or ellipses.
Pyramids and cones are both kind of similar but also very different. You can say that the cone has no vertex (something that may be confusing because of what a book says) but a cone really does not have any vertex because there are no line segments or faces that are only faces (the circle is both a base and a face) You can say they are similar because they both have only one base Hope this helped - Harry