RMS value of current that a breaker can carry in a fully closed condition without damage, for the specified time interval

is its ability to withstand the effect of electromagnetic forces of the making current of a circuit breaker.

the highest number of short-circuit current that the breakers are capable of breaking under specified conditions

The rated normal current of the circuit breaker is the RMS value of the current with which the circuit breaker shall be able to carry at rated frequency and at rated voltage continuously