The North Atlantic Treaty Organization (NATO) was much more significant during the Cold War than it is today. However, it continues to have at least symbolic importance in the history of the world.
NATO was created in 1949. It was an alliance between the US, Canada, and most of the nations of Western Europe. This alliance was directed at the Soviet Union. The point of the alliance was to deter Soviet aggression by guaranteeing that an attack on any NATO nation would be taken as an attack on all NATO nations. Thus, NATO was an important part of the Cold War. It was important because it demonstrated the resolve and unity of its members and it warned the Soviet Union not to try any aggression in Western Europe.
With the end of the Cold War, NATO is no longer nearly as relevant as it once was. However, it is still important in that it symbolizes a strategic partnership between the various countries of the West. The ties between NATO countries are one of the reasons that countries like Ukraine and Georgia want to join. NATO is seen as a good way to become connected to the US, Canada, and countries of the EU.
Thus, NATO has been an important part of world history because it has served to symbolize the connection between North America and Western Europe.