It is a triangular prism.
A right triangular prism has two identical faces. Two faces may or may not be identical in an oblique prism, in which the lateral edges are not perpendicular to the bases.
A tetrahedron has 4 faces but it doesn't look like a rectangle standing up. It is formed by 4 triangular faces.
The 3D shape you are describing is a pentagonal pyramid. It has a pentagonal base with five sides, and five vertices where the triangular faces meet. The three rectangle faces are lateral faces that connect the triangular base to the apex of the pyramid. The pentagonal pyramid is a type of pyramid with a polygonal base and triangular faces.
The solid shape that has one square face and four triangular faces is called a pyramid. If you were to have a shape that had four triangular faces and no square face, it would be called a triangular pyramid.
It is a triangular prism
The regular solid, with 20 identical equilateral triangular faces, is called an icosahedron.
A cube, like a prism has two identical parallel faces which are joined by rectangular faces (a square being a special case of a rectangle). A pyramid, on the other hand, has a number of triangular faces meeting at an apex: a cube has no triangular faces.
A triangular prism.
A right triangular prism has two identical faces. Two faces may or may not be identical in an oblique prism, in which the lateral edges are not perpendicular to the bases.
4
Triangular Prism
It has 20 identical equilateral triangular faces.
It is a triangular prism that would fit the given description
triangular-based prism
3
A tetrahedron has 4 faces but it doesn't look like a rectangle standing up. It is formed by 4 triangular faces.
The 3D shape you are describing is a pentagonal pyramid. It has a pentagonal base with five sides, and five vertices where the triangular faces meet. The three rectangle faces are lateral faces that connect the triangular base to the apex of the pyramid. The pentagonal pyramid is a type of pyramid with a polygonal base and triangular faces.