In a plane, the trajectory to a point with the same distance from a fixed line is called parabola. The fixed point is called the focus of parabola, and the fixed line is called the directrix of parabola. Parabola refers to the trajectory of a point on a plane with the same distance from the focus of a fixed point and the directrix of a fixed line. 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. In mathematics, parabola is a plane curve, which is mirror-symmetrical. When the direction is roughly U-shaped, it can be applied to any of several seemingly different mathematical descriptions, and it can be proved to be exactly the same curve.

Parabolas have the property that if they are made of materials that reflect light, the light that propagates parallel to the symmetry axis of the parabola and hits its concave surface is reflected to its focus, regardless of where the parabola is reflected. On the contrary, the light generated from the point light source at the focus is reflected into a parallel beam, so that the parabola is parallel to the axis of symmetry. Sound and other forms of energy will have the same effect.