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 the original writer. For example: to add clarification:
https://www.englishclub.com/writing/punctuation-square-brackets.htm
Parentheses or Brackets With Surrounding Punctuation. Treat parentheses or brackets and the words inside them as separate from the rest of the sentence. Any sentence that contains a parenthetical element should still make sense if the element is removed. Meena (studied all night for) the grammar test. Meena studied (all night) for the grammar test.
https://www.grammarly.com/blog/parentheses-and-brackets/
Parentheses and Brackets. Parentheses are punctuation marks that are used to set off information within a text or paragraph. Outside the realm of emoticons, parentheses always come in pairs. They can enclose a single word, a phrase, or even an entire sentence.
https://www.grammarly.com/blog/parentheses-and-brackets/
Parentheses and Brackets. Parentheses and brackets must never be used interchangeably. Parentheses. Rule 1. Use parentheses to enclose information that clarifies or is used as an aside. Example: He finally answered (after taking five minutes to think) that he did not understand the question. If material in parentheses ends a sentence, the period goes after the parentheses. Example: He gave me a nice bonus ($500).
http://www.grammarbook.com/punctuation/parens.asp
Commas could have been used in the first example; a colon could have been used in the second example. The use of parentheses indicates that the writer considered the information less important—almost an afterthought. Rule 2a. Periods go inside parentheses only if an entire sentence is inside the parentheses.
http://www.grammarbook.com/punctuation/parens.asp
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 the original writer. The two teams in the finals of the first FIFA Football World Cup were both from South America [Uruguay and Argentina].
https://www.englishclub.com/writing/punctuation-square-brackets.htm
Square Brackets or Brackets. 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 the original writer. For example: 1  to add clarification:  The witness said: He [the policeman] hit me..
https://www.englishclub.com/writing/punctuation-square-brackets.htm
Parentheses and brackets must never be used interchangeably. Rule 1. Use parentheses to enclose information that clarifies or is used as an aside. Example: He finally answered (after taking five minutes to think) that he did not understand the question.
http://www.grammarbook.com/punctuation/parens.asp
Brackets, sometimes called square brackets, are most often used to show that words have been added to a direct quotation. Sometimes, when quoting a person or document, adding a word or two is necessary to provide enough context for the quote to make sense.
https://www.grammarly.com/blog/parentheses-and-brackets/
Parentheses and brackets are used to enclose and set off material from the main text. Although writers usually need only one set of parentheses or brackets at a time, for more complex material they may need an enclosure within an enclosure (referred to as a double enclosure in this post).
http://blog.apastyle.org/apastyle/2013/05/punctuation-junction-parentheses-and-brackets.html
when do you use brackets
You can use brackets to enclose and set off material from the main text. Brackets are used to enclose and set off material from the main text.