Bonneville America Forums Forums Technical Forums General Tech Carb balancing??

I have been reading some of the post about the cheap carb balancing tools to make at home. Last year I changed my set up, and saw it was recommended to balance your carbs after making mods. Could somebody explain to me the mechanics of what's up with the balancing. Like what makes them out of balance? What difference does it make/symptoms the bike shows? And if they are out of balance after testing then what the heck do I do?
Thanks-Brett