Short answers, pulled from the story.
A bog is a wetland that accumulates peat from dead plant material, often mosses and typically sphagnum. It forms in poorly draining lake basins in cooler northern climates, where acidic, low-nutrient water and low oxygen slow decay so peat builds up over centuries.
A bog receives most of its water and nutrients from precipitation, making it always acidic and nutrient-poor. A fen receives mineral-rich surface or groundwater, so it ranges from slightly acidic to slightly basic. Alkaline mires are called fens.
The world's largest wetland is the peat bogs of the Western Siberian Lowlands in Russia, which cover more than a million square kilometres. Other large peat bogs include the Hudson Bay Lowland in North America and the Magellanic moorland in southern South America at some 44000 km2.
Bogs preserve bodies because of low oxygen levels combined with high acidity and tannic acids, which create anaerobic conditions that halt decay. The Tollund Man in Denmark was so well preserved when found in 1950 that the discoverers thought it was a recent murder victim.
Dried peat is used as a fuel, providing more than 20% of home heat in Ireland and burning in Finland, Scotland, Germany, and Russia. It is also sold as a soil amendment called moss peat or sphagnum peat, used as mulch, and used by Islay distilleries to dry barley for Scotch whisky.
Undisturbed bogs function as carbon sinks, storing carbon in peat that would release carbon dioxide if it decayed. The peatlands of the former Soviet Union were calculated to remove 52 Tg of carbon per year, and rewetting drained peatlands may be one of the most cost-effective ways to mitigate climate change.