Short answers, pulled from the story.
A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is control. A garden can incorporate both natural and artificial materials.
The word garden traces through Middle English gardin and Anglo-French gardin or jardin, of Germanic origin, akin to Old High German gard and gart, meaning an enclosure or compound, as in Stuttgart. The words yard, court, and the Latin hortus are cognates, all referring to a defined enclosed space.
The earliest recorded Chinese gardens were created in the valley of the Yellow River during the Shang dynasty, between 1600 and 1046 BC. They were large enclosed parks where kings and nobles hunted game or grew fruit and vegetables.
The Wine Pool and Meat Forest was a feature of Shaqui, a garden built by the last Shang ruler King Zhou. A large pool was filled with wine, and a small island held trees hung with skewers of roasted meat. Later Chinese philosophers and historians cited the garden as an example of decadence and bad taste.
Gardening was not recognized as an art form in Europe until the mid 16th century, when it entered political discourse as a symbol of the ideal republic. The imagery drew on the Garden of Eden, a time of abundance before hunger or property disputes.
The French formal garden, the jardin a la francaise, used parterres, geometrical shapes and neatly clipped topiary to force nature. The English landscape garden, the jardin a l'anglaise, let plants and shrubs seem to grow naturally without artifice and left nature undisturbed.
Gardens contribute to climate change through carbon dioxide, methane, and nitrous oxide, produced by over-cultivating soil, burning garden waste, running power tools, using peat, and applying excess nitrogen fertilizer. Gardeners can help prevent it by planting trees and perennials, composting garden waste, avoiding peat, using hand tools, and using nitrogen-fixing plants.