Section 18, lsattr and chatter.

This section was difficult for me to understand, am I reading it correctly?

"Extended Attributes associate metadata not interpreted directly by the filesystem with files. Four namespaces exist: user, trusted, security, and system. The system namespace is used for Access Control Lists (ACLs), and the security namespace is used by SELinux. Flag values are stored in the file inode and may be modified and set only by the root user."

Is this saying that extended attributes are used to associate metadata to files that lie outside of the attributes the file-system itself provides and is able to interpret? How do namespaces relate to extended attributes? Can attributes be set in each of these namespaces? Can an attribute exist in multiple namespaces with the same key and different values or are attributes assigned to a namespace? Are flag values extended attributes or something else?