It simply sends your input to the chat server. What happens after that depends to a large extent on your own browser and its settings. This contains links to helpful information. The information is displayed in the main chat frame. Clicking the Show Chat link will restore the chat frame.
Any regular chatter can have their details listed here.
The main idea is to indicate the times at which you generally check in. You can include a short bio. Give you Home page URL if you have one. This shows a list of people who have 'said' something. The time since they said it is shown in seconds.