Ok kiddo, let me explain.
You see, a long time ago, there was a special group of people called the Catholic Church. They had a way of doing things during their church services that was very old and traditional. But then, one day, a very big meeting happened in the 1960s called the Second Vatican Council.
During this meeting, the Catholic Church decided that they wanted to change some things about how they did their church services. They wanted to make it more modern and easier for people to understand. So, they made some new rules and guidelines about how the church services should be done.
However, some people didn't like these new rules and wanted to keep doing things the way they had always done it before the meeting. So, they decided to keep using the old ways of doing church services.
These old ways are called preconciliar rites, which means they are the way things were done before the Second Vatican Council meeting. Some people still use these old ways today, even though the Catholic Church wants everyone to use the new rules they made.
But it's important to remember that both ways are still a part of the Catholic Church and people can choose to worship in the way that feels right to them.