So, Joshua is a man who is leading a group of people called the Israelites. They are trying to conquer a place called Canaan, which is a land promised to them by God.
One day, Joshua and his army are fighting against five kings in a place called Gibeon. The battle is going well for the Israelites, but the sun is starting to go down and they need more time to finish the fight.
So, Joshua prays to God and asks for the sun and moon to stop moving in the sky, so the day won't end and his army can keep fighting. And miraculously, the sun and moon stand still in the sky until the Israelites are victorious.
It's a really cool story about how powerful God can be, and how he helps his people in times of need. And it shows that Joshua was a very faithful leader who trusted in God's power.