What does Genesis 9:18 mean?

When humanity filled the earth with sin and violence (Genesis 6:5), God destroyed it with a flood (Genesis 7:4). Only Noah and his family were spared (Genesis 7:1). Their salvation came in the form of a wooden container—an ark—which was built according to God's design (Genesis 6:11–22). In the prior passage, God delivered a promise to those who came off of the ark. God would never again destroy the world using a flood (Genesis 9:11). This promise was made not only to the humans on board, but also to the animals (Genesis 9:9–10). The sign given by God to commemorate this covenant is the rainbow (Genesis 9:12–13).

Mankind's primary responsibility, now, is to repopulate the earth (Genesis 9:7). In verses 18 and 19, Scripture records the new genealogies which will produce the rest of the human race. Noah's sons, Shem, Ham, and Japheth, are reintroduced to set up the story that will follow. Ham's son Canaan is also introduced to us for the first time. He will figure prominently in the story and its aftermath as well.