A C-rate is a measurement of how quickly a battery may be depleted of its full capacity. A 1C rate means that the discharged current will completely deplete the battery in one hour.
This corresponds to a discharge of 100 Amps of electricity for a battery with a capacity of 100 Ah.
This battery has a 5C rate of 500 Amps and a C/2 rate of 50 Amps. Similarly, an E-rate reflects discharge power. A 1E rate is the discharge power required to completely drain a battery in one hour.