A cone section is a plane curve that results when the surface of a double circular cone is intersected with a plane (cf. Figure 1).
The double circular cone is created by rotating a straight line around an intersecting axis . The mantle of the cone then consists of the totality of all straight lines (the so-called surface lines) that result from the very rotation of around . The position of the intersection surface in relation to the lateral surfaces determines which conic section is created.