Writers use brackets to add information to a sentence without changing the meaning of the sentence.
Brackets are very similar to parentheses but aren't as common, and are only used in special cases.
Rule #1: They are used to clarify or comment on the quotation.
"Four score and seven [today we'd say eighty-seven] years ago..."
"Bill shook hands with [his son] Al."
Rule #2: Brackets can be used to add something into a sentence that was taken out by the writer.
"Many sheeps [ships] left the port"
Rule #3: In formal writing, brackets are often used to maintain the integrity of both a quotation and the sentences others use it in.
"[T]he better angels of our nature" gave a powerful ending to Lincoln's first inaugural address.
In the original writing the "t" on The was not originally capitalized because it came mid-sentence.
Payton talked to her boyfriend Hayes
Maddy drove 80 miles per hour on the highway
He Lorenzo is a great chef
They Wade and Grady are graduating soon
. No longer willing to wait for the bus stop, Charles left it to find a subway station.
[Everyone] is ready for graduation
. The dog Clyde once saved someone from drowning
Buddy my dog is scared of everything
[Ray] is always thinking about climbing
Mrs. McClain likes to run with [her dog]