CHG= Caucasus hunter gatherers that split away from Western European Hunters (WHG) gatherers (who are related to Cro-Magnons) about 45,000 years ago and stopped contacting Early Neolithic farmers (ENF) about 25,000 years ago. We (as of now) think that the IVC and BMAC was made by CHG migrants or migrants very closely related to the CHG populations. Found among Iranic and Caucasus state populations and in South Asia as well (though this is also found as a common substrate in Europe, but that will be explained later).
WHG = Western Euro Hunter gathrer- form the basal part of the atlantic populations, were swarthy but had blue eyes. Form a large part of Western and Southwestern European ancestry.
EHG/ANE = Siberian tribes from the mesolithic and neolithic period that combined with populations of CHG and WHG (more CHG than WHG) to make the Yamna people (Proto- Indo-Europeans). The presence of CHG as a substrate in the Yamna means that CHG found its way into European populations via the spread of the Yamna Aryans. Present in all Indo-European populations, but peaks in Russia and Scandinavia.
SHG = Scandinavian Hunter Gatherers, a subset of WHG which somewhat mixed with ANE people earlier on, but were much closer to WHGs than to EHG/ANE. They are thought to be the first people in the world to have the combo of blonde hair, fair skin and blue eyes. After the Yamna population mated (largely Yamna men + SHG women) with the SHG, the fair genes became more common among Proto-Indo-Europeans. Peaks in Scandinavia (duh).
ENF = Early Neolithic Farmers of Levant. They are not closely related to either WHGs or CHGs or EHGs for that matter. Form the majority of ancestry of the modern day Near eastern + North African.
EEF = Early European Farmrs who are mutt combos of ENF + WHG. They form a large part of South-East Europe's ancestry.
IHG = Indian Hunter Gatherers who separated away from all non-IHG populations over 45,000 years ago. Peaks among Andaman populations and is higher in South India than in North India. They seem to be somewhat closely related to Austronesian people.