Brackets (parentheses) are punctuation marks used within a sentence to include information that is not essential to the main point. Information within parentheses is usually supplementary; were it removed, the meaning of the sentence would remain unchanged.
What is the use of parentheses?
Parentheses are used to enclose incidental or extra information, such as a passing comment, a minor example or addition, or a brief explanation. The writer may choose to put additional information within parentheses or to set off the text using dashes or commas.