When you listen to music, you hear different sounds all mixed together. Sometimes, there are some sounds that don't really belong there, and they can be annoying. We call those sounds "noise."
Imagine you are playing with some toys and you accidentally drop a couple on the floor. That's like when a musician makes a mistake or something goes wrong in the recording process, and you can hear it in the music.
Also, sometimes there's a background noise that comes from the environment where the music was recorded. For example, if a bird is singing outside the window during the recording, you might be able to hear it in the music. That's because the microphone that was used to record the music picked up the bird's sound too.
Some people like noise in music because they think it sounds cool or unique. But others don't like it because it can be distracting and take away from the parts of the music they actually want to hear.