Bokeh is the out of focus or blurry areas of a photograph. The wider the aperture a camera is shooting on, the softer the Bokeh is. In this cool DIY video, Matt from Make Magazine, shows an easy way to add a little flair to your pictures by creating custom shapes for your bokeh. Although everyone seems to break out this technique with stars and hearts around Christmas time, as Christmas lights are a great light source for this technique, here are a few more creative examples.
Or, If you'd like a little more extreme example, Gramatik uses the effect in their dubstep video "Solidified"