Okay, so a long time ago, there was this man named Abraham. God talked to him and promised him that one day his family would become a great nation and that they would be very special to Him. So, Abraham's family had children, and their children had children, and they all became the Jewish people.
God chose the Jewish people to be special to Him because He loved them and wanted them to help other people know about Him. God gave the Jewish people special laws to follow, like the Ten Commandments, to help them live good lives and honor Him.
Being the "chosen people" doesn't mean that the Jewish people are better than anyone else. It just means that they have a special relationship with God and a special purpose in life. It's kind of like when your mom says you're special to her because she loves you a lot and wants you to do good things in life.
So, the Jewish people are called the "chosen people" because God chose them a long time ago to be special to Him and to help spread His goodness and love to others.