A single nucleotide polymorphism (SNP) is a common type of genetic variation involving a single base change at a specific position in the genome. SNPs are widespread throughout the genome and can occur in both coding and non-coding regions. Depending on their location, they can affect gene function, influence disease susceptibility, or serve as neutral genetic markers. SNPs are often used in association studies to link genetic variants with traits, diseases, or drug responses. They are one of the primary types of variants represented in VCF files and are crucial for population genetics and evolutionary studies.