Genesis 18 is a story in a book called the Bible. It tells the story of three strangers who came to visit a man named Abraham. Abraham was sitting outside his tent when he suddenly saw the three strangers. He was happy to see them and offered them a place to rest and some food and drinks.
One of the strangers told Abraham that his wife Sarah, who was very old, would have a son in a year. Sarah was listening to the conversation and she laughed because she did not believe it. But the stranger said "why did Sarah laugh? Nothing is impossible for God".
After the strangers finished eating, they said they had to leave. Abraham walked with them for a while, and then the strangers told Abraham that they were going to destroy a place called Sodom because the people were doing bad things. Abraham was upset and asked if they would destroy the city even if there were 50 good people in it.
The stranger said they would not destroy the city if they found 50 good people. But Abraham knew there were not many good people in Sodom, so he kept asking if they would still destroy it for smaller numbers of good people. Eventually the stranger agreed that they would not destroy the city if they found just ten good people.
Genesis 18 tells us about how Abraham was kind and welcomed strangers into his home. It also shows that God can do anything, even if it seems impossible, and that it is important to be a good person and follow God's commandments so that we can help others and make the world a better place.