A genotype represents two alleles. When two alleles are paired together, they are considered a genotype. When these alleles show up physically on an organism, they are then considered the phenotype. For example, two sets of two alleles for brown hair (dominant) and blonde hair (recessive) would be Bb and BB. B being the dominant brown color and b being the recessive color reprensted by upper and lower case. The dominant color would show up so this person would then have the coding for brown hair.
Hoped I helped!