For people who use Mail on their Mac, or even those who simply use common email services like Gmail, have encounter Quote Level.
When a text from an email is sent from one person to another it is usually portrayed in a given color to separate it from the text of the new email, so that the recipient does not get confused as to what the person has written and what the last person has written. This is especially important for group emails or listservs where they may be dozens of people responding and it is important to differentiate the messages. The color of the text is actually the Quote Level, a color that may show how many times it has been sent. This feature has now been ported over the iPhone as of the iOS 5, yet you can turn the text you are writing into the Quote Level colors yourself. This is a good option if you want to quote text that someone else has written and have the recipient automatically know that they are reading quoted text.
If you want to add this Quote Level you can do this on the text is the email. Go into Mail and begin a new email, or initiate a response. Write out a piece of text and then press and hold on it, in the same way you would if you were to copy the text. Hit the right facing triangle on the right to show options beyond the regular. If you go over a couple options, such as the insert of photos or video, you will get Quote Level.
You will then get the option to Decrease or Increase. If you select to Increase it will change the text to a blue color, indicating that it has been quoted. A bar will also show up to the left of it, indenting it. This will show that it has been quoted as well, giving the impression that it is separated from the rest of the text. You can keep adding quote levels by going over the same process several times, each time adding an indention bar and changing the color. If you choose to Decrease the Quote Level it will then go backwards a color and remove and indention. You can do this until it represents the Quote Level you are looking to portray in your email.