It is a set of HUDs that display cooldowns, buffs, debuffs, resources, and specialization-specific modules, for several classes. There is almost no customization available : it is designed so that you just have to install it, and play your character, without spending time to setup all your "auras". But you can disable some modules if you want (by typing the slash command "/ecf").
I'm interested in any suggestion on how to improve the addon, for example if you have ideas to better organise the many, many icons.