Deuteronomy is a part of the Bible and tells the story of the people of Israel, who were special to God. It starts with them wandering in a desert for many years, and then finally getting to a new land that God promised them. In the beginning of Deuteronomy, Moses, their leader, reminds the people of all the amazing things God has done for them and tells them to obey God's rules.
In Deuteronomy 1, Moses is talking to the people just before they enter the new land. He reminds them that they used to be slaves in Egypt, but God helped them escape and has been taking care of them ever since. Moses also reminds the people how they sent spies into the new land to see what it was like.
The spies came back and told them that the land was beautiful, but there were also many strong and scary enemies living there. The people became scared and didn't trust God's promise that they would be able to conquer the land. This made God sad and angry, and he punished the people by making them wander in the desert for 40 years, until all the adults who didn't trust him had died.
Now, Moses is talking to the new generation of Israelites who are ready to go into the new land. He wants them to remember their past mistakes and to trust God no matter what. Moses tells them to be brave and to obey God's commands, so they can live in the new land and be blessed by God.