A triangular pyramid.
It is a hexahedron
A triangular pyramid has 4 faces and has 6 edges
A triangle based pyramid (tetrahedron).
You have to count the lines on a solid figure
There is no solid figure with only four edges. The smallest solid figure is the tetrahedron, made up of four triangular faces, but it has six edges.
A triangular prism
A basic pyramid with three sides?