Wikipedia describes Bokeh as,
In photography, bokeh (Originally /ˈboʊkɛ/, /ˈboʊkeɪ/ boh-kay — also sometimes heard as /ˈboʊkə/ boh-kə, Japanese: [boke]) is the blur, or the aesthetic quality of the blur, in out-of-focus areas of an image. Bokeh has been defined as “the way the lens renders out-of-focus points of light”. However, differences in lens aberrations and aperture shape cause some lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting—”good” and “bad” bokeh, respectively. Bokeh occurs for parts of the scene that lie outside the depth of field. Photographers sometimes deliberately use a shallow focus technique to create images with prominent out-of-focus regions.
Bokeh is often most visible around small background highlights, such as specular reflections and light sources, which is why it is often associated with such areas. However, bokeh is not limited to highlights; blur occurs in all out-of-focus regions of the image.
Far too technical for me. For those interested, this is how I did it. The lights in the background are from a set of hazel branches which have LED’s attached to them and were about 4ft away from the Rose, which is in the foreground. Natural light was flooding the rose from the left hand side and I decided not to use flash or any other form of lighting.
As post-processing is allowed for the 52 challenges I re-coloured the image using Topaz Re-Style.