A coppice is a traditional form of
woodland management, cutting trees back to
stumps repeatedly and harvesting the new growth some years later. The trees themselves thrive on this, and live much longer than they would if left untouched.
Most of the hardwood trees of Britain regenerate well from stumps, whereas conifers would die. I don't know how generally true this is of trees around the world, but it is vitally important for the ecological history of Britain, a densely-populated island. The history of the world, indeed, could have been very different if Neolithic farmers had launched their agrarian revolution by cutting down all the trees for firewood and farmland: no great oaks, no mighty ships, no British Empire perhaps.
But coppicing has been practised from Neolithic times. Almost all the everyday uses of wood can be supplied by quite young growth: farm tools, fences, furniture, and houses are made from branches, withies, sticks; from five years old for small objects to well-grown but still only thirty years old for beams. It was only a few great projects such as cathedrals and naval ships that needed 200-year-old oaks to be felled. Most surviving woodland in Britain is the product of a thousand years or more of continuous management; the tradition was threatened and partly fell into disuse with the Industrial Revolution, and is being revived today.
A coppice is divided into a number of coupes (or coups; I don't know whether to pronounce these as coop or cowp: aha, wertperch tells me it's usually cowp). These are regions at different levels of growth. The oldest coupe is ready to cut down and become the youngest, and the coupes are thus rotated. Cutting down tall growth opens up the floor to light and allows a diverse ecology to colonise the ground: the existence of different-height stages allows diversity of life (bird, insect, fungus, mammal, flower) to find niches whatever the conditions they like.
The stump of the hardwood tree in a coppice is called a stool. Dormant buds below the cut are reactivated: normally they would be of little use to the plant, as (except for a few trees like limes) they prefer to direct their resources to leaves up in the canopy. With the canopy gone, the whole vigour of the tree is redirected to buds on the stump. (Some species sprout up from their roots.) These therefore now grow up around the stump, and are called poles. They produce the characteristic appearance of coppiced woodland, with multiple trunks growing from near the ground. In time, if coppicing is abandoned, they can grow to full-sized trees, but the multiple trunk is a sure sign of its history.
The number of coupes and the number of years of rotation vary with the purpose of the tree: the willow might be harvested for its flexible withies after only three years; the hazel after seven for fences, hurdles, poles, and thatching struts; and construction woods like oak after twenty or thirty years.
In the Middle Ages, and especially with the growing need for very large timbers for ecclesiastical and naval purposes, the practice arose of allowing some trees, usually oaks, to grow uncut. These standards rose high up, concentrating much of their growth in strong, thick trunks, because their coppiced neighbours inhibited them from developing lower branches. Indeed, there was a technical distinction between timber, the main wood of the standards, and wood, the everyday underwood from coppice poles and from branches of timber trees.
In addition to being used to make things, such as tools, fencing, and housing itself, in a domestic capacity, coppiced wood was a primary source of fuel. Not only directly as firewood (some trees, such as hornbeam, were most suited for this), but it was partly burnt to make charcoal, the main smelting fuel before the invention of coke in the Industrial Revolution.
Coppicing fell into desuetude with altered farming practices in the nineteenth century, and with alternative forms of fuel. Woodland ceased to be so valuable economically. If timber was needed, it could be clear-felled from a plantation. Today management practice has turned around again, and the ecological richness of natural woodland in different stages of decomposition and growth is appreciated.
The cleared area is a great temptation to several predators who would take over if allowed. Of the animals, deer are the most voracious, and of plants birches. A newly cut area left to its own devices would be overwhelmed by birches after a few years, so the process of thinning is important: not all young growth can survive, so in managing the coppice some are culled to allow others room to breathe. Birch are aggressive, and have to be thinned heavily.
A woodbank is a boundary dyke of upraised earth and a surrounding ditch, traditionally used to enclose a coppice and help keep deer out. Woodbanks are often of great antiquity and today may be regarded as a kind of ancient monument, to be preserved in their own right. Another form of boundary was a hedgerow partly composed of the trees themselves, layed (sic) down, that is trained to fold over and adjoin a neighbour.
Sources: endless walking around my own local coppices, with their information about how they're being managed; together with some jolly informative material at
http://handbooks.btcv.org.uk/handbooks/content/section/3703