Okay kiddo, so there was a big fight called the Warsaw Uprising that happened during World War II in a city called Warsaw, in Poland. The people who lived there were fighting against some mean soldiers who were trying to take over their city.
During the fighting, some of the people who were fighting on the side of the people of Warsaw made a special symbol called the "Cross of the Warsaw Uprising." It's kind of like an X shape with a funny bend in it.
This cross became a really important symbol for the people of Warsaw, and for Poland too. It reminds them of the brave fighters who stood up for their city and their country during a really tough time. They use it to remember the people who gave their lives in the fight against the mean soldiers.
Even today, people still use the Cross of the Warsaw Uprising to show that they are proud of their city and their country, and they remember the brave fighters who stood up for what was right.