The analytical formula of parabola is y = a (x-h) 2+k, and the trajectory from a fixed point in the plane to a point with the same distance from an alignment is called parabola. The fixed point is called the focus of parabola, and the fixed line is called the directrix of parabola.

A parabola refers to the locus of a point on a plane with the same distance from a fixed point F (focus) and a fixed line L (directrix). It has many representations, such as parameter representation and standard equation representation. It plays an important role in geometric optics and mechanics. Parabola is also a kind of conic curve, that is, the curve obtained by the intersection of a conic surface and a plane parallel to the generatrix. Parabola can also be regarded as quadratic function image under proper coordinate transformation.