A pyramid-like 3D-object, with 4 triangle elements is called tetrahedron (Tetrahedral Element).
In simulation tetrahedrons are used to build a volume mesh.
In a first step the surface of a part will be meshed using triangle elements.
The triangle elements will be used as a base for the first layer of tetrahedrons going into the part.
Depending on the size and orientation of the base triangle element tetrahedrons with a critical aspect ratio can be created.
The random orientation of a tetrahedron elements lead to a not preferred direction.
This can lead to longer computation times.