Quantitative Trait Loci, or QTL, are specific regions on chromosomes that are associated with the variation of quantitative traits in organisms. These traits, such as height, weight, or yield, are influenced by multiple genes and environmental factors. By identifying QTL, researchers can better understand the genetic basis of these traits and how they are inherited. The study of QTL involves mapping these loci through statistical analysis of genetic data, often using techniques like genome-wide association studies (GWAS). This information can be valuable in fields like agriculture and medicine, where improving traits in crops or understanding complex diseases is essential.