need some clarification with the chat system

on the store page i install the chat plugin and the main idea behind it is that i want to give customers to chat with people that is selling stuff on the site. when someone goes online where is it going to show that someone is online? is it the buddypress widget that say who's online or in the chat widget the screen is divided in half with who is online in one side and the chat on the other side. any clarification please?