A haplogroup is a group of similar haplotypes that share a common ancestor with a single-nucleotide polymorphism. A haplotype is a group of alleles in an organism that are inherited together from a single parent. Thus, a haplogroup is a combination of alleles at different chromosomal regions that are closely linked and that tend to be inherited together, from one parent.

In human genetics, the haplogroups most commonly studied are Y-chromosome (Y-DNA) haplogroups and mitochondrial DNA (mtDNA) haplogroups, each of which can be used to define genetic populations. Y-DNA is passed solely along the patrilineal line, from father to son, while mtDNA is passed down the matrilineal line, from mother to offspring of both sexes. Neither recombines, and thus Y-DNA and mtDNA change only by chance mutation at each generation with no intermixture between parents’ genetic material.

For more information, go to Wikipedia: https://en.wikipedia.org/wiki/Haplogroup#:~:text=More%20specifically%2C%20a%20haplogroup%20is,a%20single%20line%20of%20descent.