Confirm and agree to negative questions [duplicate]

on the internet I read the following explanation: "we aren't using "no" to agree, we are using "no" to CONFIRM the negative statement."

Does that mean you confirm a negative question with no and agree with yes? That somehow seems strange to me?

An example of what the OP is asking about (as I understand it) would be:

Alice: "Didn't you hear about the party?"

Bob: "No, I didn't hear about it."

Here, Alice's question is in the negative. Bob says "no", but this actually confirms that he didn't hear about the party. If he wanted to say that, contrary to what Alice suggests, he had heard about the party, he would say "Yes, I did."

I agree, this is kind of weird.

More examples at http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv330.shtml