This is an instance of a concept.
Deer belong to the Cervidae family. The deer that visited my garden is probably a Capreolus capreolus.
Our garden is not so large that we have deer living in it, but during the Covid-19 crisis, we all work at home and are sometimes surprised by the animals we see in our gardens. One day, standing up after a lengthy video call, I had to look twice before believing my eyes, a deer was standing in our garden. Even more surprisingly, it stayed there all day and only left again in the evening.
Part of our garden we leave in a natural state, to support wildlife. The deer felt much at home. As it had antlers, I assume it is a male animal.
Damage to the garden caused by deer can be substantial. Deer eat about anything that lives in a garden, e.g. berries, shoots of trees and shrubs, young leaves etc.