I have a blackberry pearl 8130 series and i dont know what the D next to the checkmark in outbox means?

So after i send a messege to this one person (it sends) and then 5 mintues later it shows a little black d next to the check that shows that it sent....what does that mean?? the person has the same carrier as me so does it mean that he opend it?? i really need to figure this out...please help!|||the D means that the message was delivered|||d for delivered successfully!