MCCB( moulded case circuit breaker),VCB(vacuum circuit 
breaker),ACB(air circuit breaker) all are of different 
types of breaker with same 
functioning. name given them according to arc quenching 
medium used inside the breaker i.e. air,vacuum,oil,sf6 etc.
all of them are used to isolate the electrical circuit by 
manually as well as automatically to trip at the time of 
fault in line and thus save the 
circuit from damage and isolate unhealthy part from 
healthy one.
if the circuit is of low(voltage & current basically in
domestic wiring and for low rating machinery)rating we can go 
ahead with MCCB or MCB. 
but for high (voltage &current)rating circuit we go for 
costlier Breaker that is 
ACB(air circuit breaker)or VCB(vacuum circuit breaker),OCB
(oil circuit breaker),SF6 etc. because they are more 
reliable 
As on today a new trends came in practice and MCCBs are also
manufactured in low rating current previously MCCBs
manufactured not less than 63 Amps.