What does Genesis 11:1 mean?

Genesis 11 returns to a narrative where the world of man has not yet scattered across the earth into the nations, tribes, and languages described in chapter 10. Chapter 10's focus was broad, and looking far into the future, many generations from the end of the flood. The actual division of nations, as described in the Bible, will not happen until after humanity is divided by language and scattered across the globe. This event happens here, in chapter 11, at the Tower of Babel.

The descendants of Noah's three sons, Shem, Ham, and Japheth, remained together for a while, then migrated away from the region around Ararat, where the ark settled. It makes sense, given this context, that humanity continued to have one language and to share the same words, or common speech. Only one people group existed on the earth, and they all shared the same culture. Unfortunately, this led to almost the same problem which happened prior to the flood: a unified humanity can use that unity for sin, something God does not plan to allow (Genesis 11:6).