A triangular pyramid. It has triangles on its 3 sides and a triangle on the bottom for a base.
A 3D shape with one base and three faces can only have triangular faces.
A triangular base pyramid would fit the description.
The simplest such shape is PYRAMID.
A 3D shape with all triangular faces can be a tetrahedron pyramid.
A triangular pyramid.
This would be a triangular prism.
square based pyramid