These emoticons have become so popular, that many chat programs, including iChat, allow you to add them by selecting them from a list. Instead of the keyboard characters, the chat program will add a smiley face icon that corresponds to the emotion you want to convey.
To use emoticons in iChat, first open up a conversation window. Whenever you want to add an emoticon in your message to the other person, select it from the Emoticons list that appears at the bottom of the window where you type your messages. The Emoticons list is displayed as a smiley face with a downward facing arrow next to it.