Proofreading symbols are used to mark errors and suggest corrections when editing a text. Those symbols can be divided into two categories: punctuation and grammar.
Punctuation symbols are used to suggest corrections or additions to the punctuation of a text. These include the insertion of missing punctuation marks, such as commas or periods, and the replacement of incorrect or nonstandard punctuation. Examples of such symbols include a slash mark (/) for insertion of a comma, a full stop/period mark (.) for adding a period, and an exclamation mark (!) for inserting an exclamation point.
Grammar symbols, on the other hand, are used to suggest changes in the grammar or structure of a text. These symbols usually include arrows, circles, carets and boxed letters to indicate what corrections need to be made. Some examples of grammar symbols include the deletion of a word (a closed circle placed at the beginning of the word), a suggestion of a word change (an arrow between two words) or an addition of a word (a caret placed at the beginning of a word).