Bokeh

Bokeh (derived from Japanese, a noun boke, meaning "blurred or fuzzy") is a photographic term referring to the appearance of out-of-focus areas in an image produced by a camera lens using a shallow depth of field

Bokeh is especially important for large-aperture lenses, macro lenses, and long telephoto lenses because they are typically used with a shallow depth of field. Bokeh is also important for medium telephoto "portrait lenses" (typically 85–150 mm on 35-mm format) because the photographer would typically select a shallow depth of field (wide aperture) to achieve an out-of-focus background and make the subject stand out