What do these [mean] in writing?

Question

I've never known what purpose [ ] these square parentheses possess. Every sentence in newspapers and books that has those needs the words in them to make sense.

Thanks in advance.

Answer 1

it means they dont understand what you are trying to say

Answer 2

I've always used them to set numbers apart in a list, otherwise they are the same as regular parentheses.

Answer 3

[ ] means that the word(s) inside were not originally in the book/newspaper but edited in to make sense

Answer 4

The words in the parenthesis add a little more explanation to the writer's point of view.So the reader grasps the exact idea which the writer wants to convey.