emoticon is a term that evolved in internet culture from mailing list and usenet users.
During the early days, someone [anyone have more details here?] used the ASCII string :-) to indicate a smile.
Since that time, many emoticons have evolved [someone want to put some urls here to emoticon encyclopedias - preferably freely distributable ones??]
In recent years, several of the graphical messaging clients have added a graphical touch - converting ascii strings typed by the users into some icon.
Tkchat recently added this functionality. Some of the emoticons it supports includes:
:-( :^( :( - cry
8-( 8^( 8( 8-| 8^| 8| - growl
LOL - laugh
>:( >:-( >:^( - mad
:-o :^o :o :-O :^O :O - surprise
:-) :^) :) - smile
:-D :^D :D - big smile
<:-) <:^) <:) - dorky smile
8-) 8^) 8) - smiley with glasses
- smiley with tongue
;/ ;-/ ;^/ :/ :-/ :^/ 8/ 8-/ 8^/ - smirk with glasses
:-p :^p :p :-P :^P :P - smiley with tongue, 2
(: (^: (-: - upside down
;-) ;^) ;) - wink
There's a few holes in the table above because I was unable to determine what triggered the icons.
BBH notes that version 42 supports a /smile command (or /smiles /smiley /smileys) to display a window with all the emoticons & which ascii triggers them