Parentheses
Brackets
noun, する verb, の adjective
The fasten arcs are arcs that go around something to fasten these things all together. What are these things? They are (parentheses) and [brackets].
かっこ
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own. Also, watch out from the shortening.
左の括弧を読む時は単に「括弧」と言いますが、右の括弧を読む時は「括弧閉じる」と言います。
When people read the left bracket, they just say "kakko," but when they read the right bracket, they say "kakko-tojiru," which means "close bracket."