Roseli & Jacob - Shot at f/4.0 at 1/500th of a second.
When you have a photo of something that is in the foreground while the background is out of focus, or blurry, the quality of that blurry background is known as bokeh, (pronounced boh-kay). The term comes from the Japanese term "boke" which means blur or haze. Bokeh occurs when the background of t
he photo is outside the depth of field. Shallow focus techniques are often used to create images with prominent out-of-focus regions, especially when doing portraits. The reason bokeh is discussed in photography is because when you have a subject in the foreground that is sharp and in focus, having a pleasing soft focus, creamy background is less distracting, and does not draw your eye away from the subject.
I believe that the reason people are attracted to photos with bokeh, is that it is something that our eyes simply do not see in real lift. When we look at scene in which we view for example someone standing in front of background who is a good 20+ feet away, our eyes automatically focus on both the person and the background and everything appears to be in focus. We can certainly switch our focus back and forth, and whatever we're not focusing on will appear a bit softer. But when we look at the scene as a whole, then everything appears in focus.
In order to achieve pleasing bokeh generally happens when using large aperture lenses (f2.8, f1.8, f1.4 etc). See my blog post on aperture priority for more info.
Annabelle - Shot at f/4.0 at 1/100th of a second.
Cowgirl - Shot at f/5.6 at 1/250th of a second.
Alan the graduate - Shot at f/3.5 at 1/200th of a second.