No tags :(
Use brackets to enclose words not essential to the meaning of the sentence. Usually brackets contain words that add information, clarify or explain.
Use brackets to enclose:
The crew of seven (the maximum allowed) will all race tomorrow.
References or authorities cited
The dictionary (Concise Oxford) is a good guide.
Directions in the text
The firm’s sales rose by ten per cent (see attached tables).
Numbers or letters in lists
1) Introduction a) Introduction (i) Introduction
Note: A better way is to use a period. 1. Introduction or A. Introduction
Square brackets 
Use square brackets to set off words or figures used within round brackets.
Use square brackets to enclose:
Non-essential information within round brackets
The revised insurance policy covers all the company’s marine craft (powered boats [including steam] and sailing boats) against fire.
Note: This is often clumsy and you should try to rewrite the sentence.
To show any editorial comment added
He said, “The new officer [Mr James] should arrive today.”
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