Okay, kiddo. So, Salzburg is a place in Austria and Protestants are people who have a different way of practicing religion than the majority of people in Salzburg.
A long time ago, there was a law that said everyone in Salzburg had to practice the same religion as the leaders of the region. The leaders were Catholic, which means they believed in a different way of doing things than Protestants.
But some people in Salzburg didn't like this law, because they wanted to practice their religion the way they liked. So, they protested against the law and asked to be allowed to practice their own religion.
That's why these people are called Salzburg Protestants - because they were protesting the law that made everyone have to practice the same religion. They wanted the freedom to practice their own religion.
I hope that makes sense, kiddo. Is there anything else you want to know about Salzburg Protestants?