An echo is like when you shout into a big, empty room and hear your own voice come back to you. It’s as if the room is talking back, but really, it’s just your voice bouncing off the walls. Imagine throwing a bouncy ball against a wall; the ball comes back to you because it hits the wall and changes direction. Your voice does the same thing in an echo.
Think of an echo as a game of copycat with sounds. When you say something, it repeats back to you, just like when you play with a friend who copies everything you say. This happens when your voice travels and hits something like a mountain or a building, and then comes back to you.
An echo is also like a mirror for sounds. Just like how a mirror shows you your reflection, an echo lets you hear your voice again. When you talk, the sound waves travel until they hit something that sends them back to you. That’s why when you’re in a big open space, like a canyon, you can hear your voice echoing back.