What does Outbox mean on a cellphone?

Okay, Well I sent a message or tried to send a message and I could've sworn I sent it but then it was in my outbox. What does this mean exactly. I also have a Samsung At%26amp;t phone if that helps.|||I have a samsung for at%26amp;t and the outbox is a place where you create a message that might be a reply to someone's text that you haven't sent yet. It stays there until you want to send it. Hope this helps!|||it means the message is in the middle of sending, of failed. once it sends it goes to the sent items folder|||Your outbox will have copies of messages you've sent.