In-service banners and flags are a part of a very important tradition in honoring those that have served in The United States Armed Forces.
The blue star banner is flown by those who have a member of their family serving in active duty for the United States military. It is defined by a white field surrounded by a red border with a typically blue star for each family member serving. Each banner can have up to four stars per banner.
Some in-service banners are gold star banners representing a family member that has passed away during their service. For example, if someone has three family members serving, one of which has passed, they would have two blue stars and one gold star.