At first glance, a finch is not remarkable--nothing more than a small bird that resembles a sparrow. Darwin categorized 14 different species when he visited the islands in 1831.
Natural selection is the theory, generally credited to Darwin, that only the strongest of a species survive, thereby passing on traits that strengthen the species in general.
Millions of years ago, the finches arrived in the Galapagos, perhaps blown by winds.
The extreme isolation of the Galapagos Islands allowed the finches to develop through natural selection without interference from the outside world.
Darwin's theory of natural selection proved correct by the observation that 14 varieties of finches developed from the original arrival. Each finch species is differentiated by how their beaks have adapted, over the eons, depending upon which island environment they inhabited.