Almost certainly they meant to write “intended”.

lol.. I meant that intended :). BeOS made heavy use of extended attributes. Everything was a file, and you could add attributes. With modern filesystems, this is also possible, but what made BeOS so special is that the attributes were a core feature of the OS.

The file manager Tracker (Finder / Explorer) allowed you to select any attribute as a column name. The filesystem indexed all attributes, so it was blazing fast.

For example, all emails were stored as regular files (like Maildir). They had attributes for things like: MAIL:from, MAIL:when, MAIL:subject etc.

It's a different from using a separate indexing service like Spotlight.