what does that have to do with the price of tea in China?

What does that have to do with the price of tea in China? Is an expression that is asking the other person what they have just said because of how it is completely unrelated to the topic at hand. For instance if one specific topic is brought up and the other person brings up a fact or statement about something completely unrelated to the topic, they might respond with asking what it has to do with the price of tea in China.