Three sound file types are necessary because not all HTML5 audio tag enabled browsers support all audio file formats.
The third parameter should be 1 when you want to display user list (0 otherwise) and fourth parameter will decide where will user list be placed (‘right’, ‘left’ or ‘top’).
Fifth parameter will decide will smilies be displayed (1) or hidden (0).
Generally the lower you go with timing options the more stress is put to your server but your chat is more responsive.
Default values are optimal so please don’t go overboard with making them much lower.