Hi
for example if u add two numbers in binary form and there is 8 bit numbers if there is a bit that comes out from adding last bits(sign bits) that bits is carry bit.or in other words every entrance bit from adding brev bits to next position is carry in bit and every bt that goes from adding two bits to next step is carry out.but in the last bits if u have carry in and dont have carry out or u havent carry in but have caryy out in this situation overflow occurs.this means that the result isnt true.