Evolution is the change of both nature and frequency of heritable characteristics of biological populations over succesive generations. It is the process by which the differential reproductive success of living beings allow their adapatation to their environment, as well as increasing biodiversity.
Natural selection is the different reproductive success of living beings. Some organims happen to be better adapted to their environment, hence having a higher chance of survival until reproduction, by which the same traits that made them succesful will be passed on to later generations. In terms of natural selection, that is the definition of the "fitness" of an organism. No matter how healthy, resilient or capable a life form is, if it fails to reproduce, it is deemed unfit and its traits will not be chosen by natural selection.
Genetic drift happens when the heritable traits of a group are not representative of the larger population. It is the change of the frequency of a population due to sampling errors.