Bokeh...

Bokeh is a term used in photography and refers to the aesthetic quality of the blur produced in the out-of-focus areas of an image. In photography, bokeh is often considered to be visually pleasing, and is often used to create a sense of depth, isolation or emphasis on the subject. As is often the case, a high level DSLR camera and especially a lens that is capable of a 1.8 or 1.4 aperture produces the best Bokeh.

This is a great technique when there are light bulbs behind your subject such as Christmas lights on a tree or other types of light.

One trick to get good Bokeh is to be at a normal distance from your subject, focus on that subject but then increase the distance between your subject and lights.

Bokeh is influenced by a number of factors, including the lens aperture, the distance between the subject and the camera, and the shape of the aperture blades. Lenses with wide apertures, such as f/1.4 or f/1.8, can produce a shallower depth of field and more pronounced bokeh.