as said above to take track of the amount of users that joins and parts then writes it straight either to a flat file or sql so that it can be used on a website then to tell users how many users are on the channel at the time
for example, if there were 15 users in the channel it would be displayed something like "Chat Now" (Currently 15 users)
Sorry for the delay in the response to this, only just tested it. When a user joins the channel it updates the amount thats currently on, but when a user parts the channel it doesnt update the file and keep it to the higest amount of joins on that channel.