The bokeh effect refers to blur or a blurry quality, and in photography it is a very recognizable technique. The word bokeh translates from Japanese as ‘blur’.
Bokeh tends to appear in the areas of an image that remain outside the focal region. Because of this the most common technique used to add it is a shallow depth of field created through a wide open aperture. It is generally considered pleasing for your eyes and your perception of a photograph, because it can add softness to an otherwise harshly lit photograph.
This website shows the different types of bokeh effects that can be achieved:
My own examples:
I raised the ISO no higher than 400 and had aperture open wider to allow a shorter shutter time.