What are emoticons?

"An emoticon is a small piece of specialized ASCII art (usually two to five characters, always on a single line) used in text messages as informal markup to indicate emotions and attitudes that would be conveyed by body language in face-to-face communications. They are intended to be relatively simple to type, easy to recognize, and most commonly represent stylized facial expressions although occasionally other representations or imagery are also used.
With the advent of richer media in modern instant messaging and sophisticated web-based BBS systems these are often replaced in the display by a small graphic image (usually based on the generic smiley, although other evocative imagery such as hearts are also used)."
Source and further information:
http://en.wikipedia.org/wiki/Emoticons

Things like :) :P :-( :D 8) [:)

They are little pieces of computer art designed to portray the tone of your comment. (since it is hard to know if someone is being serious or lighthearted just from the text)

Emoticons are the smiley faces that are used in IM-ing and other things

The little smiley things and signs indicating emotions you can add to messages in IM or email. :) that is an emoticon meaning a smile.

check this out how funny