Okay sweetie, have you ever seen a toy that spins round and round, like a top? It spins so quickly that it gets blurry and then it slows down and eventually stops. Pralaya is kind of like that spinning top.
In Hinduism, pralaya is a time period when the universe goes through a cycle of creation and destruction. Just like a top that spins and eventually slows down, the universe goes through periods of birth, growth, decline, and decay until it eventually collapses and everything is destroyed - this is called pralaya.
During this time, everything in the universe, including stars, planets, and even living beings, get destroyed. But don't worry, sweetie, just like the top can be spun again to start over, the universe goes through another cycle of creation after pralaya.
So, in short, pralaya is a time when the universe gets destroyed, but it's not the end of everything because the cycle of creation and destruction keeps on going.