Natural selection is a process of adaptation by an organism to the changing environment by bringing selective changes to its genotype or genetic composition.
Artificial selection, also called selective breeding, is the process where humans identify desirable traits in animals and plants and use these traits to develop desirable phenotypic traits by breeding.
Some examples of natural selection include the selection of long-necked giraffes and the changes in the size and shape of beaks of birds according to their feeding habits.
Some examples of artificial selection include dog breeding to produce new breeds of dogs and cross-breeding in cash crops like wheat and rice.