Battery Terminology

C-rate.  The C-rate of a particular cell is nothing more than a way to characterize the amount of current needed to charge or discharge a cell in about 1 hour.  A 1-C rate impleis full discharge or charge in 1 hour.l  In theory, charging a cell at a 2C rate would double the charge current and cut the time in half.  In practice however, doubling the C-rate does not quite cut the time in half and,in many cases, can cause damage to the battery.  Its kind like force feeding.  You probably will get faster charging but there may be degradation concerns that start to become more noticeable as the C-rate rises. 

SoC or State of Charge.  The state of charge of a given cell, or battery, is just an estimated percentage of where, between some minimum and maximum charge levels, the battery is current at.  Think of it like a gas gauge.  Its an indicator of how many electrons are left in the tank.