Jay W. answered 05/30/19
English Tutor Specializing in Grammar and ESL
If you're talking about writing, we don't use [brackets]. Brackets are typically used in scientific or mathematical writings. Instead, we use (parentheses) as an aside comment or an explanation to a concept. They functions like informal commas.
Here are some examples:
-My brother (who is incredibly annoying) got suspended from school today.
-Gorillas are herbivores (an animal who only eats plants).