Smileys (also called Smilies or Emoticons) are stylized representations of a human face, usually displayed as yellow buttons with two dots for t

he eyes, and a half mouth. Smileys are often used in WordPress Plugins. By default, WordPress automatically converts text smileys to graphic images. When you type ;-) in your post you see Wink Icon when you preview or publish your post.

Related article: Using Smilies

Reference http://codex.wordpress.org/Glossary