So basically, in the Catholic Church there is a group of important people called bishops who help the Pope take care of everything. Sometimes, they have big meetings called synods where they talk about important things like how to help people and how to make the Church better.
During the synod, the bishops listen to each other and talk about what they think is important. They pray and study together so they can make good decisions to help the Church and all the people who go to it.
Sometimes, the Pope asks for a synod to be held so the bishops can talk about a specific topic that he thinks is important. Other times, the bishops themselves ask for a synod because they want to talk about something that they think is really important.
Overall, the synod is a really important part of how the Catholic Church works and helps the bishops work together to make good decisions for the good of everyone.