What is meant by emasculation? When and why does a plant breeder employ this technique?

The process of removal of the anthers before they mature from a bisexual flower carefully using the forceps without affecting the female reproductive part (pistil) is called emasculation.

It is one of the measures of artificial insemination.

To obtain a plant of desired variety, the plant breeders use this technique. They protect the stigma from being pollinated by undesired pollens from the same flower.