It is a form of artificial hybridisation, whereby the desired pollen grains are generally used for pollination in order to develop plants with many desirable characteristics.
Artificial hybridisation includes techniques like emasculation and bagging.
Emasculation is also done to prevent self-pollination and thereby support cross-pollination.
Removal of anthers from flower bud before dehiscence of the anther is called emasculation.
Bagging is also a technique of covering the stigma with bags to prevent contamination of stigma from pollens. This technique is mainly practiced to ensure pollination with pollen from the desired male parents during the breeding program.