apropos-read-pattern is an autoloaded compiled Lisp function in `apropos.el'.

(apropos-read-pattern SUBJECT)

Read an apropos pattern, either a word list or a regexp.
Returns the user pattern, either a list of words which are matched
literally, or a string which is used as a regexp to search for.

SUBJECT is a string that is included in the prompt to identify what
kind of objects to search.