Okay kiddo, imagine you are playing a game of tag with your friends. Just like you can hear someone running up behind you, planes and helicopters have special sensors called missile approach warning systems that can tell when a missile is coming towards them.
When a missile gets too close, the warning system sends an alert to the pilot so they can take action to protect themselves and their plane. This may involve launching flares or trying to evade the missile.
Missile approach warning is very important because it helps keep pilots safe and prevent dangerous situations in the air. Just like how you need to be careful not to bump into things when you're running around, planes need to be careful not to be hit by missiles.