Bokeh is defined by Wikipedia as: In photography, bokeh is the blur, or the aesthetic quality of the blur, in out-of-focus areas of an image, or "the way the lens renders out-of-focus points of light." Differences in lens aberrations and aperture shape cause some lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting— "good" or "bad" bokeh, respectively.
Basically, it's the idea that you use the blur to bring out the focal point of your pictures (with greater or lesser amounts of success). Here are a few of my better bokeh pictures...
What I absolutely love about this one is that the bokeh creates the effect that the flower is just floating in space. There is a stem... but you can't see it!
|Turaco, Busy Building|
This is a White Crested Turaco from the free-flight section of Brookfield Zoo.
|Little Bug Makes an Exit|
In this one, not only is the background blurred, the edges of the petals on the left are too, drawing your eye to the center of the flower and the bug crawling out of it.
|Mr. Fokker Poppy Faces the Sun|
|Itty-Bitty Flower Committee|
|Shiny Red Wings|
This guy is from one of my recent Midewin posts. The beetle is in sharp focus, as is the leaf he's on, but the rest of the plant, and the plants behind him are almost nonexistent. Because of all the soft greens, his red shell really pops.
|Halloween Pennant in August|
Dragonflies like this are pretty well camouflaged, so if the background were to stay as busy as it really was, the dragonfly wouldn't be nearly as visible or clear.