Email is the primary form of person to person communication on the Internet. A disadvantage to email is that it doesn't convey emotion very well. Sarcasm and very rude comments look exactly the same. Consequently, emoticons have developed.
Emoticons are little smileys that convey the emotion missed by face to face communication.
There is even a Smiley Dictionary . Another disadvantage to email is that if you don't know someone's address, you probly won't find it. An advantage to email is that it is asynchronous. Two people don't have to get together at the same time to communicate via email. Its similar to leaving a message.