When things are synchronized, they happen at the same time or in a way that matches each other.
Synchronized things are like a dance or a song where everything happens together and looks very good.
Examples:
The dancers moved in a synchronized way.
We need to synchronize our watches.
The synchronized swimmers moved together in the water.
The birds flew in a synchronized pattern.
The synchronized lights and music made the show amazing.
The team synchronized their steps perfectly.