It refers to the group of animals, plants, and other organisms sharing the same geographical region or habitat.
There are different habitats and microclimates within a biota, so, within a biota, organisms live in different Niches.
Example-
The biota of a forest includes all animals, plants, insects, and microorganisms living in that particular forest.
Soil biota includes all the soil microorganisms, soil animals, and plants though they live in different niches like they use different parts of soil as their habitat.