Whats the difference between the Message Sentbox and Outbox?

[sunspun]

Hi-I was trying to look up a PM that I had sent to someone recently, and didn't see it in my Sentbox, even though I knew I had sent it. Then I saw that there was also one called the Outbox, so I looked in there, and there were 4 messages in there, all of which I thought I had sent. What's that box for? Does this mean I didn't ever send those after all? Is it like a Drafts folder? Because I can see that the ones I send are automatically saved into my Sentbox - so why were these put in my Outbox?Mainly I just need to know if I ever sent them or not. Do you know?
Thanks!

[FairCasinos]

The messages that haven't been read are in the outbox. Once the person has read the message, it goes to the sent box.