all living things (except people) that are undomesticated
"chemicals could kill all the wildlife"
Animals, plants, and fungi, not normally domesticated, often to the exclusion of plants, fungi, fish, insects and other invertebrates, and microscopic plants and animals; hence
"The park rangers spent their morning monitoring wildlife populations to ensure they were recovering after last year's fire."
In plain English: Wildlife is all the animals and plants that live in nature without human help.
"We went on a hike to see the local wildlife in their natural habitat."
Usage: Wildlife refers specifically to animals living in their natural habitat rather than those kept as pets or livestock. While it can sometimes loosely include wild plant life, it most commonly denotes non-domesticated fauna such as deer, birds, and fish found in the wild.
The word wildlife is a straightforward combination of the words wild and life. It entered English simply by joining these two existing terms to describe animals living in their natural state.