Operational security is a way to protect secret or important things from bad people who might want to steal them or harm them. It's like keeping a treasure hidden from pirates so they can't find it.
For example, if you have a secret password, you don't want anyone else to know it. You have to be careful not to tell it to anyone or write it down where people can see it. This is called keeping it a secret or "opsec" for short.
In the same way, companies or the government have important information that they don't want just anyone to know. They use operational security to protect this information by making sure only the people who need to know it have access to it. They might use passwords, security cameras, or other special technology to keep it safe.
Operational security is important because bad people can cause a lot of trouble if they get access to information they shouldn't have. So, it's like a secret game of hide and seek where you have to be smart about keeping things hidden and safe.