An emergency population warning is a message that helps people know what to do if something bad is happening in their area. It can be given in different ways like on the television, radio, or through loudspeakers, so that everyone can hear it.
An emergency can be like a bad storm, fire, or another kind of danger that could cause harm to people or buildings. The warning will tell people what they should do to stay safe, like staying inside or moving to a safer place. It will also tell people where to get help if they need it.
It's kind of like when your parents tell you to put on your seatbelt when you get in the car, so that you stay safe if there's an accident. An emergency population warning is like a reminder to everyone that something bad might happen and they need to be prepared.