When you read reviews about lenses, you will often see the word Bokeh mentioned. No, it is not a misspelling of the bouquet. Bokeh is an optical spectacle that makes the bright out-of-focus look more aesthetically pleasing. In the world of photography, this is really important.
To achieve the effect, you use a fast lens when you photo busy backgrounds. Used at a wider aperture, it makes objects in the background appear to be blurred. The level of Bokeh is determined by the number of blades in a diaphragm. When the number is higher, the objects in the background appear more circular. The technique is often used in nature and still photography.