Short answers, pulled from the story.
The Pontic Caspian Steppe stretches from the northern shores of the Black Sea to the Caspian Sea. It covers northeastern Bulgaria, southeastern Romania, Moldova, southern Ukraine, and the North Caucasus region of Russia. The territory extends into western Kazakhstan where it joins the Kazakh Steppe.
Genetic research identifies this region as the most probable place where horses were first domesticated during prehistoric times. Bronze Age pastoralists known as Yamnaya spread their ancestry from 3000 BC to 1500 BC across Europe and South Asia. Earlier cultures like the Linear Pottery culture existed between 5500 BCE and 4500 BCE within these steppes.
The Kurgan hypothesis posits that the Pontic Caspian steppe was the homeland of Proto-Indo-European speakers. This linguistic group spread across Eurasia over thousands of years to become modern Indo-European languages. Genetic evidence supports the migration patterns suggested by this hypothesis regarding the origin of major language families.
Cimmerians inhabited the area during the 12th century BCE through the 7th century BCE while Scythians dominated from the 8th century BCE until the 4th century BCE. Sarmatians held power from the 5th century BCE to the 5th century CE and Ostrogoths migrated through the steppes between the 3rd and 6th centuries. Huns and Avars appeared in the historical record from the 4th to the 8th centuries before Turkic Golden Horde ruled from the 13th to the 15th centuries.
The historical landscape corresponds to current nations including Ukraine, Russia, Kazakhstan, and Romania. Today the steppe extends through northeastern Bulgaria and southeastern Romania covering Moldova and southern eastern Ukraine completely. The North Caucasus region of southern Russia remains part of this territory along with western Kazakhstan.