Short answers, pulled from the story.
The Ardennes covers large portions of Belgium and Luxembourg, and extends into Germany and France. Most of the Ardennes lies in the southeast of Wallonia, the southern part of Belgium, while the northernmost third of the Grand Duchy of Luxembourg is also part of the Ardennes, known locally as the Éislek or Oesling.
Signal de Botrange, at 694 metres, is the highest point in the Ardennes. It is located in Liège Province, Belgium, and is also the highest point in the Benelux countries.
Germany used the Ardennes as the primary route for its mechanised invasion of France in 1940, exploiting Allied assumptions that the terrain was impassable for armoured forces. The crossing, carried out in two days under Erich von Manstein and Heinz Guderian, led to France's fall on the 25th of June 1940. The Ardennes was also the site of the Battle of the Bulge in December 1944, Germany's last major offensive in the west.
The Ardennes takes its name from Arduenna Silva, the name used in the Roman period for the ancient forest. Arduenna probably derives from a Gaulish root related to the Welsh ardd and Latin arduus, both meaning "high" or "steep," with the second element possibly related to the Celtic word for "fair" or "blessed," suggesting an original meaning of "forest of blessed or fair heights."
The Ardennes forests supplied charcoal that fuelled the first furnaces in Belgium's Wallonia region, supporting an industrial period in the 18th and 19th centuries during which Wallonia became the second industrial power area in the world after Great Britain. When coal replaced charcoal in metallurgy, the industry shifted to concentrate around coal mines near cities including Liège, Charleroi, and La Louvière.
The Ardennes were raised during the Givetian age of the Devonian period, approximately 382.7 to 387.7 million years ago, as part of the Hercynian orogeny. The region has continued to be uplifted in more recent geological time by a mantle plume, with the greatest uplift concentrated in the east where the Ardennes meets the Eifel.