Okay kiddo, imagine you have a group of friends playing a game called "Pirates". You all pretend to be pirates sailing a big ship in the sea.
Now, let's say one of your friends is really good at leading the group and always knows what to do next. The other friends really look up to this leader and always listen to what they say.
In the real world, this is kind of like what the Command at Sea Insignia is for the Navy. It's a special badge that a person gets when they are really good at leading a group of sailors on a big ship in the sea.
They have to go through a lot of training to learn how to be a good leader and make important decisions quickly. When they earn this badge, it shows everyone else that they know what they're doing and can be trusted to lead others on a ship.
It's kind of like a "Captain" badge in your "Pirates" game. It means that person is in charge and knows what to do to keep everyone safe and get the ship to where it needs to go.