Structural means that it something is genetically or environmentally programed into people and they can do nothing to help it. This idea is called determinism, where humans do not have control over their environment or genes. Behavorial is free will. Humans can and will do the best they can to achieve the best place and circumstances for themselves. They are not exposed to any enforced circumstances.

Every organisms has a genotype. In humans this is the set of 25,000 genes we carry that code for the embryo to grow and develop into a mature adult. Each organism gets two alleles per gene out of all possible alleles there are for each gene. For example blood type has three alleles A, B, and O. Each person inherits only two of the three possible. The phenotype are the gene’s alleles that are active and alter some of the organism’s measurable differences: height, weight, coloration, rate of metabolism or blood type. If the person gets A O then they have a phenotype of A because the O doe not alter the phenotype. If one of a gene’s alleles is not expressed in the phenotype it makes no difference to the individual’s behavior or appearance but it might in another generation. In another generation the O allele might pair with another O.