Simple definition
procfs is a virtual Linux filesystem exposing process and kernel status through paths under /proc.
Purpose and use
procfs exposes kernel and process information as a virtual directory tree, usually mounted at /proc.
How does it work?
Entries reflect current state; some interfaces also permit parameter changes subject to permissions and configuration.
Example and verification
Interpret process information in its namespace context and account for access restrictions.
Points to watch
It is not an ordinary directory to copy as a backup. Some entries expose sensitive information or lack a conventional file size.
In short
procfs is an interface to live system state.