here.itrelates to the charge or dischare rate in relation to its total capacity. a 1C charge rate means you can put the entire capacity of the batter back into it in 1 hour. same as a 1C discharge means you can run a load bigh enough to discharge that entire battery in 1 hour with out hurting it. so in a 100 amp battery if it has a 1C charge rate you can use a 100amp charger on it with out dammage , as for discharge you can put a 100amp load on it with out dammaging it.
li has a higher than 1C rate but most BMS will limit to 1C for even longer life and extra insurance.
Steve