A cubic surface in real 3-dimensional space is the set of zeros of a
polynomial of degree 3 in three variables. Considering the corresponding
"complex projective" surface yields a classification of double
points. There are conic double points, biplanar double points
B
3, B
4, B
5, B
6, and three kinds
of uniplanar double points. Explanations can be found in Schilling's
catalogue, and in chapter 2 of the commentary edited by Fischer, cf.
References (RE).