Nato stands for the North Atlantic Treaty Organization. It is an organization made up of 29 countries, including the United States, Canada, and many countries in Europe. Enlargement of Nato means that more countries are joining the organization. This means that more countries have agreed to work together to help keep their countries safe and promote world peace. When a country joins Nato, it promises to help defend the other countries in the organization if it is ever attacked. All of the members of Nato also agree to help each other by discussing and working together on different issues.