What is "warichu"

Warichū (割注 or 割註, sometimes 割り注, literally “split annotation”) is the Japanese word for the traditional East Asian typographic device of typesetting in small double lines editorial comments, notes, parenthetical comments, and other annotations that may or may not belong to the text proper. It is used for the same kind of text which in English would be placed between parentheses or brackets, or in footnotes. The word “warichū” itself is used in some computer programs that deal with " CJK" typesetting, and in discussions about CJK typography.