Parenthesis
Definition
Grammar. a qualifying, explanatory, or appositive word, phrase,clause, or sentence that interrupts a syntactic construction without otherwise affecting it, having often a characteristic intonation and indicated in writing by commas, parentheses, or dashes, as in
William Smith—you must know him—is coming tonight.
William Smith (you must know him) is coming tonight.
William Smith, you must know him, is coming tonight.