"Now the whole earth had one language and one speech. And it came to pass, as they journeyed from the east, that they found a plain in the land of Shinar, and they dwelt there. Then they said to one another, 'Come, let us make bricks and bake them thoroughly.' They had brick for stone, and they had asphalt for mortar. And they said, 'Come, let us build ourselves a city, and a tower whose top is in the heavens; let us make a name for ourselves, lest we be scattered abroad over the face of the whole earth.' But the Lord came down to see the city and the tower which the sons of men had built. And the LORD said, 'Indeed the people are one and they all have one language, and this is what they begin to do; now nothing that they propose to do will be withheld from them. Come, let Us go down and there confuse their language, that they may not understand one another's speech.' So the LORD scattered them abroad from there over the face of all the earth, and they ceased building the city. Therefore its name is called Babel, because there the Lord confused the language of all the earth; and from there the Lord scattered them abroad over the face of all the earth" (Gen. 11:1-9).
Much time has passed since Noah and his family stepped off of the ark. Man has become more and more advanced (as he was before the flood). The ability to build cities and towers out of brick and mortar was possible in their day. Their desire seems innocent enough at first - "Let us build ourselves a city, and a tower whose top is in the heavens". There's nothing wrong with building a tall tower is there? Not inherently, but read a little further. The people desire to make a name for themselves. They want to live in close proximity to one another instead of spreading out and filling the Earth (as God had commanded back in 9:1). God is described anthropomorphically as coming down to investigate. He notes that in their united state of having only one language, they would be able to accomplish anything (particularly, any evil thing they put their collective minds to). Thus, the Godhead (note the plural "Us") implemented a solution--the introduction of many languages. This change would naturally lead to smaller groups forming out of the whole (who could understand each other), and they would separate themselves from those whom they could not communicate with. The building of the tower was abandoned. No doubt the people were scared and confused when they could no longer communicate freely with everyone. Although there is no way to know with certainty, it is interesting to contemplate what may have been the original root language of humanity.
The next seventeen verses provide genealogical information for ten generations (from Shem to Abram, inclusive). Very little is known about any of these men listed in between Shem and Abram. With a little arithmetic we can observe the lifespan of man significantly diminishing during these ten generations (from 600 years down to around 200 years). Obviously, the world Shem lived in when he stepped off the ark was much different than the one Abram was born into. Besides a shortened lifespan, there would have been significant differences in overall population, languages, technology, increased wickedness (again), establishment of nations, etc.
Let us now read the remainder of the chapter:
"Now Terah lived seventy years, and begot Abram, Nahor, and Haran. This is the genealogy of Terah: Terah begot Abram, Nahor, and Haran. Haran begot Lot. And Haran died before his father Terah in his native land, in Ur of the Chaldeans. Then Abram and Nahor took wives: the name of Abram's wife was Sarai, and the name of Nahor's wife, Milcah, the daughter of Haran the father of Milcah and the father of Iscah. But Sarai was barren; she had no child. And Terah took his son Abram and his grandson Lot, the son of Haran, and his daughter-in-law Sarai, his son Abram's wife, and they went out with them from Ur of the Chaldeans to go to the land of Canaan; and they came to Haran and dwelt there. So the days of Terah were two hundred and five years, and Terah died in Haran" (Gen. 11:26-32).
There are a couple things we will comment on here. Sarai's barrenness is obviously significant, being mentioned almost as soon as we are introduced to her (and it will come up again repeatedly in the coming chapters). We learn elsewhere that Sarai and Abram were actually half-siblings (though such a sexual union was not yet forbidden at that time; cf. 20:12; Lev. 20:17). We also note here the beginning of Abram's departure from the idolatrous city of Ur to Canaan--what would soon be known as the Promised Land! Interestingly, Abram's father (Terah) was an idolater (cf. Josh. 24:2), and he made some of the journey toward Canaan with his son. This has always been curious to me in light of Acts 7:2-4.