Okay, imagine you're at school and you're putting on a play with your friends. A cue is basically a signal that someone gives you when it's your turn to do something on stage.
For example, your friend might give you a cue to enter the stage or to say your lines. It's like a little reminder that helps you know what to do next.
In a big professional theater production, there are often more complicated cues, like sound or lighting cues. These are signals for the people who work behind the scenes to make sure everything happens at the right time.
So, when you hear the word "cue" in a theatrical context, it just means a little reminder or signal to do something on stage or behind the scenes.