Twitter question: How do direct messages work?

[Rainbow Connection]

I sent a direct message. The person replied. I replied to that message. My reply went to other followers, not just to the person I originally sent the message to. I thought direct messages were only between the sender and the receiver(s). Can someone explain this?

[lovenickjonas97]

in order to not have everyone that follows you see your message, you have to hit "direct message" every time. it's annoying but that's how you keep your twitter messages private.