Traditional parametric CAD programs force the user to enter huge amounts of data without much (if any) visual control. On the other hand, CAD programs such as AutoCAD or Blender are based on a pure graphical manipulation of data. This approach allows a huge degree of freedom (you can draw anything, from the screw to the space ship), but it also imposes a very steep learning curve on the user.
Wing Helper allows you to define your construction by specifying the numerical data (parametric approach), while at the same time representing the effects of your changes visually in a "live view" window. Wing Helper is not a general purpose CAD program, it concentrates on a single task, and makes this task as simple as possible. By following this philosophy, Wing Helper combines the best of both parametric and visual worlds.