A microbiome is the sum of all microorganisms in a habitat. Such habitats are, for example, our skin, waters or flower meadows. If you choose a very large scale, you could also speak of the microbiome of the Alps or the earth.
Explanation for children:
A microbiome describes all microorganisms in a habitat. Microorganisms live almost everywhere, and most of them are very useful. For example, they live in our intestines and help us digest, or they make delicious yoghurt from milk that we can eat.