The document discusses several geometric concepts and procedures:
1) Drawing a perpendicular line through a point to an existing line.
2) Drawing perpendicular lines through exterior points.
3) Drawing angle bisectors and constructing triangles using angle bisectors.
4) Drawing medians, altitudes, and axis of a triangle and their intersection points.
5) Constructing a Feuerbach circle of a triangle through nine points.
6) Constructing regular polygons given the circumscribing circle.