An oscillator is like a toy that makes a sound over and over again. It can be a bell or a whistle or even a drum that goes "boom boom boom." The sound happens because there is something inside the toy that vibrates really quickly. Think of when you shake a toy or a bell - it makes a sound because the part inside is moving back and forth really fast.
An oscillator is just like that, but it's not a toy. It's a really important part of things like computers, radios, and even watches! It's kind of like the heartbeat of these things because it keeps everything moving at a steady pace.
The oscillators in these devices don't usually make any sound we can hear, but they're still important because they help keep other parts of the device working properly. It's kind of like when we're walking down the street and have to keep our steps in time with our friends or family so we don't trip or fall. The oscillator helps different parts of the device stay in time with each other so everything works correctly.
That's why oscillators are important, even if they might not seem like a very exciting or fun toy. And just like how we enjoy different kinds of sounds from toys, there are many types of oscillators that do different things for different devices!