Your character can display an infinite variety of emotions and facial expressions. These descriptive commands allow your character to demonstrate how he or she is feeling. They must be performed "face-to-face" however - in other words they can only be received by people in the same location as you. Hundreds of these pre-defined commands exist, each one at your character's disposal. Thus you may type GRIN and your character will do likewise; you may SMILE, LAUGH, SOB, PURR like a cat or even BARK like a dog. Many of the descriptive commands can also be directed towards specific things or individuals. As a result you are able to HUG <person> or WAVE to someone leaving your chamber.
If you find that you need a more specific emotion:
EMOTE <text> or EMS <text>.
EMOTE JUMPS UP AND DOWN MERRILY = Genesis jumps up and down merrily.
EMS HEAD HURTS = Genesis's head hurts.
Often you can use emotions to interact with the intelligent CCCs (See HELP CCC) of Avalon. They tend to understand NOD, YES, SHAKE (to shake your head), NO, GREET, HUG, SNEER and other such obvious emotions. Greeting CCCs is often interpreted as a request to be charged with an important quest.