Heterozygous refers to an organism that has two different alleles for a specific gene. Alleles are variations of a gene that can produce different traits. For example, if one allele codes for brown eyes and another for blue eyes, an individual with one of each allele is considered heterozygous for eye color. In genetics, being heterozygous can influence how traits are expressed. This can lead to a dominant trait being displayed if one allele is dominant over the other. Understanding heterozygosity is important in fields like genetics, breeding, and medicine for predicting traits and studying genetic diversity.