Emoticons are emotional messages you can communicate with keyboard characters. These are very handy when using email. It is difficult to read a person's tone in an email, but a clever smiley on the end can let the other person know you aren't miffed.
If you still aren't sure how they work, take a look at this and turn your head to the left:
It's a face with 2 eyes, a nose and a smile. Still can't see it? Turn your monitor clockwise 90 degrees. Just kidding ;-)
There are lots more on wikipedia.
How could you use emoticons? Have a splendid day! :-)