The microprocessor 8086 can be operated in two modes, minimum mode and maximum mode.

In minimum modes, all control signals are generated by the microprocessor 8086 itself. So it can be used in single microprocessor base system. In maximum mode, all control signals are generated bu the bus controller 8288 and not by the microprocessor 8086.

So, this way, it can be used in multiprocessor system, when microprocessor based system contains external math co-processor like 8087.
The pin no. 33, the, MN#/MX is used to set either minimum or maximum mode of microprocessor 8086 and also the function of pin no from 24 to 31 will be changed.