Okay, imagine you're drawing a picture with lots of little dots on it. Sometimes, when you're drawing, your hand might slip or you might accidentally draw a dot where you didn't mean to. That's called a glitch in your picture. Glitches can also happen when you're using something like a computer or a video game - something might go wrong and cause a glitch on the screen.
Removing a glitch means fixing that mistake so your picture (or your computer or video game) looks and works the way it's supposed to. Depending on the type of glitch, there are different ways to remove it. Sometimes you can just erase the dot you didn't mean to draw, and sometimes you have to use special tools to fix a computer glitch. But the overall goal is to make sure everything is working smoothly and correctly.