The figure is a pyramid and the base is a square.
Cube, aka hexahedron
A square based pyramid.
Not necessarily. The solid could be a square based cuboid (hexahedron).
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"
The answer is a pyramid.
A pyramid with a square base, or a triangular prism.
A square pyramid has 5 sides.