The three types of natural selection are directional selection, disruptive selection and stabilizing selection. Natural selection is when organisms adapt to the environment and pass down these adaptations to their offspring when they breed. Those that are not able to adapt die before breeding, putting an end to unfavorable traits.
In directional selection, one extreme value is favored over the other extreme or the mean. For example, faster animals outlive slower animals that are easily killed by predators or hunters. In disruptive selection, the average is selected against in a population. For example, light-colored peppered moths survive in rural areas, while dark-colored peppered moths survive in industrial areas. Medium-colored moths are easily seen in both areas, so very few of them survive.
In stabilizing selection, the average is favored. For example, human babies with average birth weight have a higher chance of surviving than babies that are too big or too small.