A Bezier curve in its most common form is a simple cubic equation that can be used in any number of useful ways. Originally developed by Pierre Bézier in the 1970's for CAD/CAM operations, it became the underpinnings of the entire Adobe PostScript drawing model. If you're a regular user of Adobe Illustrator, Macromedia Freehand or Fontographer, any number of spline-based 3D programs, etc., you've probably used Bézier curves.