How was the development of new territories by the Slavs?

It is known that in the period from the 6th to the 8th century, the settlement of the ancient Slavs took place, during which they were divided into two large groups: eastern, western and southern. So the tribes of the eastern settled across the territory of eastern Europe. The southern Slavs occupied the northern part of the Balkan Peninsula, while the western ones settled in the central regions of Europe.