Let me get the ball rolling:

Q. What is C?

A. C is the term used to describe Charge and disCharge rates for the batteries we use, and is equal to the Capacity of the battery pack, converted to Amps. For example, a 1200mAh battery pack will have a C of 1.2 Amps. To charge a battery at 1/10 C or C/10 means to charge it at a rate equal to one-tenth its capacity. A C/10 charge for our example 1200mAh battery pack would be .12 Amps, or 120mA.