Think of a circle as a big, round cookie. When you take a bite, the edge of the cookie is like the path of a sine wave. The sine wave goes up and down, just like the bumpy edge of the cookie after you’ve taken a few bites. The up parts of the wave are like the top of the cookie, and the down parts are like the bottom.
Imagine a playground swing. When you sit on it and someone gives you a push, you go up into the air, then come back down, and then go up again. This motion is like the sine wave, always moving up and down smoothly. The highest point you reach is like the peak of the sine wave, and the lowest point is like the trough.
Picture a sound wave. When you clap your hands, the sound travels in waves, similar to the sine wave. The loudest part of the clap is the top of the wave, and the quietest part is the bottom. Just like the sine wave, it keeps going up and down, making beautiful patterns in the air.