Jeremiah 31 is a story from the Bible about a promise that God made to his people, the Israelites. It's like when your mom or dad promises you ice cream if you behave well, but God's promise is much bigger.
God promised the Israelites that he would bring them back to their land after they were taken away as captives to another place. This would make them very happy because they loved their land and missed it very much.
God also promised the Israelites that he would take care of them and protect them as they traveled back to their land. He would be with them every step of the way and help them with anything they needed.
Furthermore, God promised that he would give the Israelites a bright and hopeful future. They would have a new start with him and their relationship with him would be much stronger than before.
Overall, the story is about God's love and goodness towards his people. He promises to take care of them no matter what happens and provide them with a bright future.