Okay, so imagine you and your friends really like playing a game together. But one day, some of your friends start playing the game differently and they make up new rules that you don't really like. You can either keep playing with them and follow their new rules, or you can decide to start a new game with just the friends who like the old rules.
Well, a really long time ago in Germany, some people didn't like the way the Catholic Church was doing things. They thought the Church was being too powerful and not following the Bible the right way. So they decided to start their own group, called Protestants. They wanted to follow the Bible and do things their own way, instead of the way the Catholic Church said they should.
Later on, a man named Adolf Hitler became the leader of Germany. He wanted everyone to be part of a big group that he controlled, including the churches. He made a new church called the Protestant Reich Church, which was supposed to be a combination of all the different Protestant groups. But a lot of people didn't like this new church either, because they felt like it was being controlled by the government and not following the true teachings of the Bible.
So, in short, the Protestant Reich Church was a church created by the German government during World War II, but some people didn't like it because they felt it wasn't following the true beliefs of their religion.