Macrohaplogroups (sometimes called supergroups) are the foundation for a number of other haplogroups. They represent older shared ancestors on the maternal tree. Macrohaplogroups link together many of the more common haplogroups that are found today.
For example, haplogroup M is found throughout Eurasia and is especially common on the Indian subcontinent. Haplogroup M is considered a macrohaplogroup because it includes the haplogroups D, C, E, G, Q, and Z as subclades.
Note: Although mtDNA naming conventions are much like those for Y-chromosome DNA (Y-DNA), they are separate systems.