This is the collective state of human reason and knowledge. Everything we know, understand, and can reason about as a species is the noosphere. It is constantly expanding as we learn more and more.
The name comes from the Greek “noos” which means “mind” or “thought.”
The noosphere is an informal term – it’s a theory proposed by several people throughout the 20th century. While the concept of collection human consciousness certainly exists, noosphere is just one name for it.