What was the yellow star used for during World War II?

Explanation

The yellow badge was a star-shaped cloth patch that Jews were ordered to sew on their outer garments by the Nazis. The shape of it was identical to the national and religious symbol of the Jews, the Star of David. Its predecessor came in 1939, when all Polish Jews older than 12 years old were forced to wear en armband with a blue Star of David on it. The yellow star was introduced in 1941 for all Jews older than six, and had to be carried on the left side of the breast. Gradually the law was extended first to all of Germany, and then across borders.