What is NATO and Its Purpose
The gist
NATO is a group of countries that work together to keep each other safe and prevent conflicts by promising to defend one another.
Explain like I'm 5
Imagine a group of friends who agree that if anyone tries to bully one of them, all the friends will help protect that person.
Big picture
NATO was created to promote peace and security among its members, especially after big wars, by encouraging cooperation and collective defense to prevent future conflicts.