Parentheses and Brackets
Both parentheses and brackets are used to set off items.
Brackets
Brackets ([ ]) are used as specialized parentheses. As a punctuation mark, brackets enclose editorial comments, corrections, and clarifications, especially when the material is quoted but also when the addition might otherwise disturb the intent of the sentence.
"There's something happening [at SEMATECH] that is a fundamental strength of America," said Robert Galvin, the keynote speaker at Presidents' Day.
Furthermore, the department anticipates additional reductions in the budget for the coming fiscal year [October 1992-September 1993].
Brackets may be used as parentheses within parentheses, although embedded parenthetical elements can often be distinguished more clearly with a combination of commas, dashes, and parentheses.
...five tools (two chemical vapor deposition [CVD] tools, one etch...
or
...five tools - two chemical vapor deposition (CVD) tools, one etch...
Brackets are used to enclose the citation of quoted or reproduced material. See BIBLIOGRAPHIC CITATIONS.
Parentheses
Parentheses are commonly used to set off related, but independent, clauses or sentences. Place the period inside the closing parenthesis if the parentheses contain the complete sentence. Otherwise, place the period after the closing parenthesis.
...meet those needs. (See Figure 3.)
...within three-dimensional circuit elements (for example, vias, trenches, and contacts).
If a clause that is normally set off with a comma is followed by a parenthetical phrase, the comma appears immediately after the closing parenthesis.
In the Main Window (the large window under the Command Menu), ....
Do not use parentheses within parentheses (except as appropriate in code or equations). Use a combination of dashes, commas, and parentheses (or if necessary, parentheses and brackets) when you need to embed parenthetical phrases.