What is the difference between self-pollination and cross-pollination?

Since flowers possess both male and female parts, some flowers can fertilize themselvesor fertilize another flower on the same plantwhich is called self-pollination. Or the ovules of one flower may be fertilized by the pollen of a different flowering plant of the same species, a method called cross-pollination. The wind, water, insects, and other animals help to carry pollen from one flower to another. Cross-pollination usually produces a better plant: the offspring of cross-pollination possesses the genetic traits of two parents, which may give it new characteristics that will help it survive in an always-changing environment. Cross-pollination is so desirable, in fact, that many flowering plants have developed different ways to keep self-pollination from happening. In the flowers of a spiderwort plant, for example, the stamens are ready to release pollen grains before the pistils are ready to accept them, so the pollen has to travel to other spiderwort plants in search of a ripe pistil.