The gut biome is composed of the contents of your gut. It is not inside you, but like the skin separates the environment from the inside of your body. There are more bacteria in your gut than there are cells in your body. If these were not kept out, you would be dead.
The gut biome keeps you healthy. We can adversely affect this biome with health consequences. We know understand that many different diseases are influence by this biome such that we get sick or unhealthy.
This is really just an introduction to the subject which will eventually occupy its own book.
