It refers to bringing the actual results closer to the desired results.
The following steps are included in it :
i) Setting performance standards,= are those criterias on basis of which actual performance is measured.

ii) Measurement of actual performance,= measurement of actual performance tells manager whether the work has been done according to the plan or not.

iii) Comparison of actual performance with standards,= actual performance is compared with the standards and deviations are found out.

iv) Analysing deviations, = deviations are analysed.
and
v) Taking corrective action = for removing the hurdles in the actual work progress correct actions are taken.

Thanks.