Perhaps you've made a tin can telephone like the one in the image. You hold one can and a friend holds the other, with the string stretched tight between. Now let's see what happens when you talk.
First, your voice makes the air move in little waves inside the can. The sound waves strike the bottom of your tin phone and make it move in and out. This movement is called vibration. The vibration of the tin can makes the string vibrate. The vibrating string makes the bottom of the other tin can move in and out. The second tin can pushes against the air and makes sound waves. The sound waves strike your friend's ear, and he hears what you are saying.
A real telephone is something like a toy phone, but it works by electricity. Electric current runs through the wire between your house and a friend's house. The current runs steadily if nothing disturbs it. But let's see what happens when you begin to talk.
Your voice makes sound waves which hit a little round plate in the mouthpiece of the phone.
The little plate vibrates, just as the tin can did. But the plate is connected with the telephone wire in a special way. When the plate vibrates, it makes the electric current travel unevenly.
The uneven current travels to your friend's receiver. There it works an electric magnet. The magnet makes another little plate move in and out. This vibrating receiver plate causes sound waves which travel to your friend's ear. And so he hears what you are saying.
