You've probably seen this kind of feature in emails before. Basicalll it's a feature where by you're notified when the recipient of your text message opens it up and reads it. The function is simple to execute, and can be very useful if you rely on text messaging for your communication.
All you do is simply type *0# at the beginning of your message. Then be sure you make a space between the character and your actual text. What will then happen is that you'll be notified when the recipient actually opens the text up. It's an added text, but again it has its uses depending on how much you rely on texting.