Okay! So, have you ever seen a fire truck with its lights flashing and siren blaring? That's the fire brigade! When we say the fire brigade is 'on a call', it means they're called to help out with something important, like a fire or an emergency.
Imagine if there was a big fire at a house, and someone called for help. The fire brigade gets a message that they need to go and help. They quickly put on their clothes and jump in the fire truck. Then, they drive as fast as they can, with the lights and siren on, to get to the place where they are needed.
When they arrive, they work as a team to make sure everyone is safe and to put out the fire. They use big hoses filled with water and special tools to help them do their job. Being on a call is really important because it helps keep people and places safe from fires!
So, whenever you hear a fire truck, remember that they're off to help someone in need!