Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a core mechanism of evolution, describing how certain traits become more common in a population over successive generations because those traits confer a survival or reproductive advantage in a specific environment. The process requires three main components: genetic variation within a population, inheritance of those variations from parent to offspring, and differential survival or reproductive success. Through these interactions, organisms best suited to their environment tend to thrive and pass on their advantageous traits, leading to gradual adaptation and the development of species over deep time.