You should do a Google search for Bokeh and you'll be fairly enlightened. A simplified way to put it (sorry if I oversimplify it) would be:
Originally Posted by mono
Bokeh is the way the out-of-focus areas of the image look when using a specific lens. Some lenses have nice Bokeh (the out-of-focus areas look nice) and some other not. Pinhole cameras have OK Bokeh (but they don't have a lens :-)
A German (like you) might ask: Why the h**l would someone care how an out-of-focus area would look when the objective is not to have out-of-focus areas on the film ? Well, the answer to that can be given by someone else...