Moment redistribution refers to the behavior of statically indeterminate structures that are not completely elastic, but have some reserve plastic capacity.
When one location first yields, further application of load to the structure causes the bending moment to redistribute differently from what a purely elastic analysis would suggest.
When the beam is indeterminate, it forms sufficient number of hinges to make itself determinate.
Further increment in load does not increase the moment at the points where the plastic hinges are formed.
The increased load increases the moment in the less stressed sections of the beam; hence due to this, further plastic hinges are formed.