A deer is a wild mammal used throughout history as a source of meat and leather (generally without informed consent on the part of the deer).
Deer were widely distributed across the period world and were the subject of hunting since pre-hisstory. Their meat (known as venison was eaten, and their hides used for clothing, as leather for boots, and for the covering of tent-type dwellings. Within period they were often treated as the preserve of the nobility, and laws were enacted making it illegal for commoners to hunt oir to harass deer. In England entire Royal forests were set aside for the cultivation and hunting of the King's deer, and savage Forest Laws enacted to protect these areas.
Deer are herbivorous ruminants, generally living in, or on the fringes of, wooded or forested areas. The deer of the Old and New Worlds are treated by naturalists as separate groups, having, it is thought, evolved from separate origins in Siberia/America and in Asia
Some deer have antlers -- bony growths on the head -- rather than the horns borne by other ruminants.
Stag -- a male deer
Buck -- a young stag
Hart -- a stag beyond its fifth year
Hind -- a female deer
Fawn -- a young (immature) deer