What is the difference between genotype & phenotype?

genotype is the genetic makeup and phenotype is the physical stuff you can see

Genotype is the genetical basis for a person.  For example a person may have the genes for brown eyes and black eyes, one from mother and the other from father, but his brown eye trait may be recessive so he will only have black eyes.  This genetic composition of a person is called genotype.

On the other hand, phenotype is the outward appearance of a person, for example black eyes is a phenotype.

genotype of an organism is a complete description of its hereditary material (usually DNA). phenotype is the expression of the genotype in the physical form of the organism.

The Genotype is the allelic combination that is present at the DNA level.  You normally have two copies of a gene at any given locus.  Having allele A and allele B you are given a genotype of AB.  

Phenotype is the physical characteristic of that allele combination.  

For instance if you have a trait controlled by one gene locus like, tall pea plants vs small pea plants with tall plants being domninate. The genotypic makeup would be TT, Tt for tall plants and tt for small plants.  The phenotypic makeup would be small vs. tall.

my shortcut of remembering the difference is that "ph"enotype is the "ph"ysical appearance.

I often differentiate by saying the phenotype is like a photo and the genotype is the genes ( letters).

While I will point out things like internal chemical reactions that may not physically SHOW like eg diabetes, or other diseases where you phsically do not see anything, but for the most part and at simple levels, talking about pheno-photos like eye colour, freckles, dimples etc are fine and work well.

THe genotype is the letter code eg AA or Aa or aa or whatever letter you are using.....the SAME letter is used for a particular trait and we call the different versions of the same gene ALLELES eg A and a or G and g...