Evolution means the process of developing by gradual changes. A rock star might discuss her evolution as a musician, for example. In biology, evolution refers to genetic change in species or populations over time.
Evolution usually refers to a process that produces a better or more complex form. In biology, it is the natural process by which animals and plants develop from their original or primitive state to their modern or specialized state. This noun is from Latin evolutio, "an unrolling or opening," combined from the prefix e-, "out," plus volvere, "to roll."