What is genotype? What is the difference between phenotype and genotype?

The Genotype is the genes, DNA nucleotide sequences contained in the chromosomes of an individual, which condition the phenotype. The Phenotypes then are a biological manifestation of genotypes, For instance, the altered hemoglobin chain of sickle cell disease and the manifestation of the disease itself are the phenotype. Altered DNA nucleotide sequence in gene that codifies the production of that abnormal hemoglobin chain is the genotype.