Emoticons are little arrangements of textual characters typed so that they look like facial expressions. These punctuation-mark faces are frequently used by participants in practically any chatroom on the Internet or on a BBS, and it is not uncommon to see :-)'s and :-('s liberally scattered through any computer-based text conversation. Nor are emoticons limited to just faces; people have managed to make dozens of other objects with just a couple of characters.
Here's a small compilation of emoticons I've seen. Feel free to e-mail me your own "punctuation creations". I've put a small emoticon creator "applet" at the bottom of this page for you to play around with.