In biological genetics the pheonotype is the observable characteristics of the organism in contrast to the genotype which is the actual gene structure that encodes it. In computational genetic algorithms there is a similar difference between the way in which the state is encoded, for example, the locations of appliances ina. kitchen, and the way that gives rise to, say, plumbing and wiring issues within the kitchen. Often the mapping between genotype and pheonotype is effectively a one-way function, where it is hard to work out the geotype given the phenotype. However, for a genetic algorithm to work it is essential that there is at least some pattern to the relationship otherwise it will be no better than a Monte Carlo techniques.
Used on page 77