Quadratic curve is also called conic section obtained as the intersection of a cone (more precisely, a right circular conical surface) with a plane.
Conic sections are exactly those curves that, for a point F (in black), a line L (also in black) not containing F and a non-negative number e, are the locus of points whose distance to F equals e times their distance to L. F is called the focus, L the directrix, and e the eccentricity.
