A cap badge is a special pin or badge that goes on a soldier's or police officer's hat. This badge is really important because it helps people to know which group or organization the soldier or police officer is a part of.
It's kind of like when you wear your favorite superhero t-shirt or soccer jersey. When people see you wearing it, they know what team you're rooting for or who your favorite superhero is.
The design of the cap badge is usually unique to the group or organization that it represents, and it often has important symbols or designs on it that are meaningful to that group. For example, a police officer's cap badge might have a picture of a shield or star on it, while a soldier's cap badge might have a picture of a weapon, animal or a sign from his/her military branch.
When a soldier or police officer wears their hat with their cap badge on it, it shows that they are part of a team, and it also lets people know who they can go to for help or protection.