Okay kiddo, let's talk about some super important people in history called the Catholic Monarchs. Do you remember what "Catholic" means? It means people who follow the religion of Christianity.
Now, the Catholic Monarchs were King Ferdinand and Queen Isabella of Spain. They were called "Catholic" because they were very religious and believed strongly in the teachings of the Catholic Church.
During their reign, which was from 1474 until 1516, they did some really big things that helped shape history. One of the most famous things they did was to support the famous explorer Christopher Columbus on his journey to find a new route to Asia.
But, they also did some things that weren't so good. They got rid of many people who were not Catholic from Spain, including Jewish and Muslim people. This is called the Spanish Inquisition, and it was a very dark time for many people.
Overall, the Catholic Monarchs were important because they helped Spain become a powerful country in Europe and they also helped spread Christianity around the world. But, we should also remember that their actions were not always fair or just.