A chain letter is a letter being forward over and over with the object being to obtain something or stop something the letter says will occur if the person who received it does not forward it on to a specific number of other people. Chain letters just take up bandwidth needlessly, and they are not real.
No, chain letters are not real. There are two types of chain letters: hoax and urban legends. Hoax chain letters are sent with the intent of defrauding the recipient while urban legend chain letters are used to threaten or scare people. http://en.wikipedia.org/wiki/Chain_letter