It is a form of punctuation that looks like this: [ ]
The use of brackets is less complicated than use of the apostrophe. Still, it is important to know when to use them. Proper use can also be very freeing to a writer. Here's the basics:
1) Use brackets to include explanatory words (the writer's own) within a quote.
For example, "Marigolds [a hardy summer bloomer] are known to repel insects from vegetable gardens," said Professor Scanolli.
2) Use brackets when you must change a word, such as a pronoun, or capitalization in a direct quote.
For example, Professor Scanolli believes every Gardener must "find [her] best strategy."
3) Important to Know! [sic] after a word indicates that in transcribing material the original author's spelling has been retained.
For example, I'm currently transcribing letters written by my aunt and uncle during WWII. They both spell the word night as nite, thus I transcribe it: Good nite [sic] my darling.
Don't overuse brackets as it becomes tiresome to the reader's eye to keep stopping at them. And be very, very careful not to abuse brackets by either a) using them as criticism of another writer's material (pointing out misspellings) or b) using them to change the meaning of quoted material.
How can brackets be freeing to a writer?
This post is brought to you by the April A to Z Blog Challenge. Check back all through April for daily discussions of writing conventions.