Heterozygotes are genes that carry contrasting inheritance factors. Each human body is composed of genes, and these usually come in pairs that are slightly different from each other. The different versions of genes are called alleles. Alleles are responsible for determining physical or notable characteristics and traits a specific person has.
For example, if your mom has a set of regular brown eyes and your dad has a set of blue eyes, you are most likely to get a dominant trait from either of them. A heterozygote gene is basically two copies of DNA that are a mix of two different alleles that come from your parents.