Mainstreet, you're right, its called bokeh. Bokeh occurs when you set the lens to its maximum aperture (smallest number) which creates a very shallow depth of field, making the background go out of focus. The best bokeh occurs when the lens either has curved aperture blades or has a high number of blades, both of which create a very smooth bokeh as apposed to lenses with fewer blades which create a more polygonal bokeh.
bokeh refers to the background blur in a photograph. the term 'bokeh' is considered cliche and it's useage is considered lame by SOME photography circles. i have no opinion on the word either way.
