A national academy is like a really special school that only the best and brightest students get to go to. It's kind of like Hogwarts, but instead of learning magic, the students learn all about science, engineering, and other really important stuff.
The national academy is usually made up of very smart people who have done amazing things in their field- scientists who have discovered new things, engineers who have built cool stuff, and researchers who have pushed the boundaries of what we know. These people are really important because they can share what they know with others and help us all learn more.
When someone is invited to join the national academy, it's a really big deal. It means that they are one of the best in their field, and that they have done extraordinary work. These people get to go to special meetings and conferences, where they can share their knowledge with other experts from all over the world.
So, think of the national academy like a club for really smart people who want to learn from each other and help make the world a better place. It's a place where scientists, engineers, and other amazing people can come together to share their knowledge and work on solving big problems.