>bog (bôg) n.
1) a. An area having a wet, spongy, acidic substrate composed chiefly of sphagnum moss and peat in which characteristic shrubs and herbs and sometimes trees usually grow. b. Any of certain other wetland areas, such as a fen, having a peat substrate. Also called peat bog.
2) An area of soft, naturally waterlogged ground.
Definition taken from dictionary.com
That definition is fine, but if you want to know more than just that, read on. A bog is a type of wetland. Wetlands compose approximately 6% of the Earth's total surface (Alumäe, H, pers. com., 19/9/00). Under the heading wetlands, there are three categories: marshes, water areas, and mires. This site is mostly concerned with mires, but I'll break down the other categories as well. Water areas include any water body up to 6m deep. So oceans don't count, but small lakes, ponds, and rivers do. Marshes are basically coastal water areas. Only 3% of the 6% in question is relegated to our area of interest, mires. Mires can then be broken down further into three types: swamps (57% of Estonian mires), transitional bogs (12% of Estonian mires), and bogs (31% of Estonian mires). These three types will be discussed in greater detail in a later section. In Estonia, the presence of bogs/mires is extremely common, and in numbers, Estonia is second only to Finland in percentage of land covered by wetlands.
Some major characteristics of bogs include low nutrient levels in the soil, an acidic pH of about 3, and a lack of large vegetation (Masing 24)