Okay, so imagine you have a really loud bell. When you hit the bell, it makes a sound that goes "ding!" and that sound travels through the air to your ears. That's kind of like a signal.
Now, sometimes when you hit the bell, it doesn't just make one sound. The sound can keep going and going, like an echo. That's called ringing.
Ringing is kind of like when you shout "hello!" in a big empty room and you hear your voice bounce back to you. Except with ringing, it's happening inside a device like a phone or a computer.
Sometimes ringing can be good, like if you're trying to listen to music on your phone and you want to hear every note clearly. Other times it can be bad, like if you're trying to listen to someone talk on the phone but there's a bunch of ringing noise in the background that makes it hard to hear them.
So, just remember that ringing is like a really long and continuous sound that can happen inside devices, and it can be either good or bad depending on the situation!