What is Biome?

Legal Definition
A biome /ˈbm/ is a formation of plants and animals that have common characteristics due to similar climates and can be found over a range of continents. Spanning continents, Biomes are distinct biological communities that have formed in response to a shared physical climate. Biomes are distinct from habitats, because any biome can comprise a variety of habitats.

A biome contrasts with a microbiome. A microbiome is also a mix of organisms that coexist in a defined space, but on a much smaller scale. For example, the human microbiome is the collection of bacteria, viruses, and other microorganisms that are present on a human.
-- Wikipedia
Legal Definition
The balance of a eco system that is naturally maintained.