Smiles is the web name for originally shorthand such as ";-)" or ":-(" that people put in their chat room text or when text messaging on mobile phones to quickly show expression. But as all technology advances with time, Smilies became initially more graphical such as
and then more animated such as
This forum uses a standard set of these Smilies, the easiest way for users to insert them into their post is when making or editing a post, in the post text window, where you want your Smilie to appear, just left button mouse click one one of the Smilies provided by the forum software in a row to the top left of the main post text window.
The shorthand for that Smilie will then be placed in your post, and, when you Save your post, the forum software will convert that standard shorthand into the graphical and sometimes animated Smilie for you.