Square brackets ([ ]) are used inside of parentheses to denote something subordinate to the subordinate clause. Here's an example from the 13th edition of ...
Square brackets (also called brackets, especially in American English) are mainly used to enclose words added by someone other than the original writer or ...
Square brackets are used, usually in books and articles, when supplying words that make a quotation clearer or that comment on it, although they were not ...
We typically use square brackets when we want to modify another person's words. Here, we want to make it clear that the modification has been made by us, not by ...