Often, we come come across photos which have a sharp subject and a dreamy smooth defocussed background! That effect is called, Bokeh! Its a japanese word for blur, or basically, the out-of-focus areas in a photo. This is an inherent effect, so nothing special needs to be done. Having a few lights on the background, makes the bokeh beautiful, and more evident.
So, open up those apertures, and shoot awesome bokeh!!
Go Bokeh!! 🙂