Copy number variation (CNV) is a significant source of genetic diversity in humans, with numerous CNVs identified through various genome analysis platforms. CNVs can be formed through recombination-based and replication-based mechanisms, with de novo locus-specific mutation rates higher than those of single nucleotide polymorphisms (SNPs). CNVs can cause Mendelian or sporadic traits, complex diseases, and may also represent benign polymorphic variants. Gene duplication and exon shuffling are prominent mechanisms driving gene and genome evolution. CNVs have been linked to complex traits such as susceptibility to HIV infection, autism, and schizophrenia. The extent of CNV contribution to human genetic diversity and phenotypes remains largely unknown, but recent studies suggest that CNVs may play a significant role in gene expression variation. The mechanisms underlying CNV formation include nonallelic homologous recombination (NAHR), nonhomologous end-joining (NHEJ), fork stalling and template switching (FoSTeS), and retrotransposition. The mutation rates of CNVs are much higher than those of SNPs, and the variable mutation rates across the genome may contribute to the varying contributions of CNVs to Mendelian loci. CNVs have been associated with various diseases, including Down syndrome, thalassemia, red-green color blindness, and neurodegenerative disorders like Parkinson's and Alzheimer's disease. They also influence complex traits such as autism and schizophrenia. The Database of Genomic Variants (DGV) currently catalogs over 38,000 structural variations, but the true extent of CNVs in the human genome remains to be fully elucidated.Copy number variation (CNV) is a significant source of genetic diversity in humans, with numerous CNVs identified through various genome analysis platforms. CNVs can be formed through recombination-based and replication-based mechanisms, with de novo locus-specific mutation rates higher than those of single nucleotide polymorphisms (SNPs). CNVs can cause Mendelian or sporadic traits, complex diseases, and may also represent benign polymorphic variants. Gene duplication and exon shuffling are prominent mechanisms driving gene and genome evolution. CNVs have been linked to complex traits such as susceptibility to HIV infection, autism, and schizophrenia. The extent of CNV contribution to human genetic diversity and phenotypes remains largely unknown, but recent studies suggest that CNVs may play a significant role in gene expression variation. The mechanisms underlying CNV formation include nonallelic homologous recombination (NAHR), nonhomologous end-joining (NHEJ), fork stalling and template switching (FoSTeS), and retrotransposition. The mutation rates of CNVs are much higher than those of SNPs, and the variable mutation rates across the genome may contribute to the varying contributions of CNVs to Mendelian loci. CNVs have been associated with various diseases, including Down syndrome, thalassemia, red-green color blindness, and neurodegenerative disorders like Parkinson's and Alzheimer's disease. They also influence complex traits such as autism and schizophrenia. The Database of Genomic Variants (DGV) currently catalogs over 38,000 structural variations, but the true extent of CNVs in the human genome remains to be fully elucidated.