Proofreading marks are symbols used by editors and proofreaders to indicate changes that need to be made to a document. The most common proofreading marks are STET, DELE, and CARET. STET stands for 'let it stand, ' meaning that the editor or proofreader is suggesting that no changes be made to the text. DELE stands for 'DELETE, ' meaning that the editor or proofreader is suggesting that the text be removed. CARET stands for 'INSERT, ' meaning that the editor or proofreader is suggesting that something be added to the text.