In Exodus 9, there was a really big problem in Egypt where these bad things called plagues were happening. The plagues made things very hard for the people of Egypt, including the animals and the plants. In this particular chapter, God sent another plague to Egypt, and it was a plague of hailstones.
The hailstones were like really big balls of ice falling from the sky, and they were really dangerous. They could hurt people and animals and even break buildings. But God told the people of Israel, who were living in Egypt, that they should keep their animals inside and stay safe while the hail was falling.
Pharaoh, who was the leader of the Egyptians, saw how bad the hail was and how it was hurting everything in Egypt. So he asked Moses and Aaron, who were leaders of the Israelites, to pray to God to stop the hail. God heard their prayer and stopped the hail from falling.
But even after this happened, Pharaoh still didn't believe in God and didn't want to let the Israelites go free from slavery. So God sent another plague, which we'll learn about in the next chapter.