You neglected to present the exact question you found... What do these signify (. * ? +) in regexp?
That is a different question than what does this regexp mean. which would find "any_character0_or_more_spaces"
() the stuff between the parenthesis is a regexp . match any character * match 0 or more of the preceding character ? match 0 or 1 of the preceding character + match 1 or more of the preceding character