What is the difference between MCB and MCCB ?

It depends on the extinction of fault current. Moduled case CB is required for higher fault current ratings to safely break the fault current. Miniature CB can be used for lower current ratings

MCB:

Rated current not more than 100A

Trip characteristics normally not adustable

Thermal or thermal-magnetic operation.

MCCB:

Rated current up to 1000A

Trip current may be adjustable

thermal or thermal-magnetic operation

MCB is having low short-circuit rating. MCCB is having high short-circuit rating.

MCCB is bigger in size in comparision to MCB.

MCB used for LV 230 V and 415 V small load  less then 63 A and MCCB used for heavy load  above 63A and provide over current and over load with earth fault 

MCBs are miniature circuit breakers with optimum protection facilities of overcorrect only.These are manufactured for fault level of up to 10KA only with operating current range of 0.5 to 63 Amps (the ranges are fixed), single,double and three pole verson.These are used for smaller loads -electronic circuits,house wiring etc.MCCBs are Moulded case Circuit breakers,with protection facilities of overcorrect, earth fault. it has a variable range of 50% to 100% operating current.They can be wired for remote as well as local operation both.They are manufactured for fault levels of 16KA to 50KA and operating current range of 25A to 630Amps.They are used for application related with larger power flow requirement.