Parenthesis: ( )
A parenthesis is one of a pair of curved marks ( ), which are used in a sentence to enclose a word, phrase, sentence, number, etc as an explanation, extra information, or a remark. The content within the parentheses is nonessential and if removed will not affect the meaning of the sentence, as the sentence by itself is grammatically complete. The parentheses can also be in the forms of brackets, dashes, or commas.
Parentheses setting off additional information in a sentence
Parentheses enclosing numbers or letters in a sentence