Genesis 5 is a part of the Bible that tells a story about the very beginning of the world. It talks about how the first people that were made lived for a really long time - hundreds of years!
It starts by telling us about a man named Adam, who was the very first person that God created. Adam had a son named Seth. The chapter then goes on to list a whole bunch of other people who were Adam's descendants, or his children's children's children, and so on.
Each person in the list lived for a really long time, like some for more than 900 years! This is way longer than people usually live nowadays - we usually live for around 70-100 years.
The chapter also gives us some information about what kind of lives these people led. It tells us who they had kids with, who their children were, and what kinds of things they did during their lives.
Overall, Genesis 5 is a way for us to learn about the very beginning of the world and the first people that lived on it.