Here's the breakdown:

* Genotype: The actual genetic makeup of an organism, represented by the combination of alleles for a specific trait. For example, "Bb" for brown eyes.

* Phenotype: The observable characteristics of an organism, resulting from the interaction of its genotype and the environment. For example, "brown eyes" is the phenotype.

In simpler terms:

* Genotype is like the code (alleles) that determines the feature.

* Phenotype is the actual feature itself (observable trait).

Therefore, the allele combinations (genotype) determine the phenotype, but they are not the same thing.