Here's an amazing page of great info to help you match your battery power to your gear ratios for the performance you're looking for. Thanks to Dark Horse RC for this valuable setup chart.
http://dhrc.rchomepage.com/RolloutCalc.htm
Balance leads and power leads on a LiPo battery pack.
On a 3S, the balance leads will be common with one ground and one power, but will have two additional leads that are independent of the primary power wires in order to monitor individual cell voltage.