How is artificial selection different from natural selection?

Artificial selection is when humans decide certain characteristics they want to in animals, e.g. high milk production in cows, so they breed them (highest milk-producing cows) together. Natural selection is when nature forces living organisms to adapt to their environment, and the best-fit (e.g. giraffes with tall necks that can reach tall branches of trees for food, or bacteria that has adapted to surviving antibiotics), survives and passes on their genes to their offspring so future generations have selected genes which are advantageous in the evolutionary perspective.