If you're asking what is bokeh, in technicaly terms, it doesn't actually mean the blurry background itself; rather, it's the quality of that blur, and the out of focus areas in the fore and ...

Bokeh is the name given to the out-of-focus blur that appears in the background of a photo. The wider the aperture of a lens (which refers to the f-stop number, like f/2) then the greater the ...