This phenomenon wherein human beings interfere in the process of reproduction to allow only selective mating with the idea of producing an individual with required characters is called breeding (as against natural reproduction)
Breeding in domesticated animals and cultivated crops has a history which perhaps began with the changed habit of human beings from the hunter gatherer stage to agricultural settlements.
A continuous attempt is made since then and continuing even now to obtain better quality animals (egg production, milk production, meat quality and quantity etc) and better quality plants (increased yield, disease resistance, early maturity etc).
With the discovery of laws of inheritance by Mendel and the development of Genetics as an important science, refined tools and techniques have been made available to the plant and animal breeder.
Earlier techniques of plant and animal breeding were a touch and go affair. The understanding provided by Genetics however has vastly changed the scenario.
Plant and animal breeders are sure of what they want to produce and how to produce the desired type of progeny.