Okay kiddo, let me explain what a nova is!
Imagine you have two very close friends who are both stars, like the sun. Sometimes, these two stars get a little too close to each other and start to pull each other's matter towards them. This creates a lot of heat and pressure, causing a huge explosion of energy! This explosion is what we call a nova.
The nova is like a big firework show in the sky! It is an incredible bright light that shines for many days or weeks. After the explosion, the two stars that caused the nova are still there, but they might be a little different than before. They may have lost some of their mass, or they might be a little bit cooler.
Scientists study novae to learn more about how stars work and how they change over time. Even though they are very far away, we can see them with big telescopes and learn a lot of cool things about our universe.