Refer to figure.
Note: This is nearly the same question as 508081, however in the UK CAA exams, feedback indicates that they reference a macroburst rather than a downburst.

Sometimes thunderstorms will produce intense downdrafts that create damaging winds on the ground. These downdrafts are referred to as macrobursts or microbursts, depending on their size:

• A Microburst is a localized column of sinking air (downdraft) within a thunderstorm. These also move outwards by reaction from the ground. The windshear (headwind to tailwind) may be between 50 and 90 kt.
  Microbursts are short-lived, usually lasting less than 5 minutes, and they are relatively compact, usually affecting an area of 1 to 4 km in diameter. Microbursts are most likely to occur in summer air mass thunderstorms in low latitudes where the surface conditions are dry - causing extreme turbulence and severe windshear conditions.
• A Macroburst is a similar even but affect a larger area - with a diameter of more than 4 km.

Both are only created by either mature or sometimes dissipating CBs, as developing CBs do not have any significant downdrafts.