Explain genetic drift?

Genetic Drift is the change in the frequency of a gene variant (allele) in a population due to random sampling of organisms.

Genetic drift is the change in allele frequency of a gene in a population over time when there is no selection on that gene.

For example, a new allele has mutated which causes the production of two blue spots on the wings of a butterfly rather than one. This has no negative or positive affect, and thus is not selected for or against. Therefore, the only driver for the frequency of this allele is chance.

Genetic drift is random and therefore does not result in adaptation.