Copy Number Variation (CNV) refers to the differences in the number of copies of specific segments of DNA among individuals. These variations can involve duplications or deletions of DNA segments, leading to differences in gene dosage, which can affect how genes are expressed. CNVs are a significant source of genetic diversity and can influence traits, susceptibility to diseases, and responses to medications. They are often studied in the context of genetic disorders, cancer, and population genetics to understand their role in health and disease.