A pyramid.
A three-dimensional shape with eight triangular faces is called an octahedron.
An octahedron
the sides of a pyramid are triangles
square pyramid
This is an Octahedron!
There is a contradiction in your question. If the base has four equal sides then is it a square so not all the faces are Triangles. However if the base is a square and the rest of the faces are triangles then your object is a "Square-based Pyramid"
A pentagon
an octagon
2 equilateral triangles
A three-sided shape is called a triangle. There are three types of triangles: equilateral triangles, iscosceles triangles, and scalene triangles. Equilateral triangles have all equal sides and angles; iscosceles triangles have two congruent legs and a base, and scalene triangles do not have any equal sides or angles.
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The answer is a pyramid.