In general, a Bézier curve is a polynomial expression used to describe a curve.
They are commonly used in computer graphics software, but they may not always be
called anything more than a curve. Generally, the user selects two endpoints and
one or two control points. A Bézier curve with one control point is called a
quadratic Bézier curve and the kind with two control points is called cubic.

### Cubic and Quadratic Bézier Curves

This example is based on

the description at Wikipedia.
A and C are the start and end points, B is the control point. The points D and E
are each half way along AB and BC, respectively. The midpoint of DE is marked F,
F is on the curve. This pattern can be repeated with A, F and D then F, C and E
to get more points on the curve. The process repeats infinitely for math, but only
as far as our eyes can see for SVG.