One of the more interesting terms in photography is bokeh (pronounced bo-keh). Bokeh is the aesthetic quality of the blur in the out of focus portion of an image. The word is derived from the Japanese word boke meaning blur or haze.
Bokeh can be an important quality photographers evaluate when choosing a lens. This is particularly true when a photographer strives for non-distracting and smooth backgrounds. Nature, portrait and event photographers for example often make use of bokeh to isolate their subjects from busier backgrounds by choosing a smaller f/stop setting and thus a larger aperture. By choosing a smaller f/stop setting a photographer chooses to narrow the plane of focus and create a shallower depth of field. By having a shallower depth of field more of the photographed scene is then placed out of focus.