Okay kiddo, let me explain what z-fighting means in a way you'll understand.
When we look at things on a computer screen, they are made up of lots and lots of tiny squares called pixels. These pixels are what create the images we see. Sometimes, when we have two objects that are very close together on the screen, the computer gets confused about which pixel should be in front and which should be behind. This is called z-fighting.
It's like if you had two pieces of paper and you wanted to put one on top of the other, but you couldn't decide which one should be on top. That's what z-fighting is like.
When z-fighting happens, it can make the image on the screen look weird and glitchy. Sometimes the two objects will flicker back and forth, like they're fighting for the front position.
To prevent z-fighting, programmers have to make sure that objects are placed in the right order and that the computer knows which one should be in front. It's kind of like organizing your toys on the shelf - you want to make sure they're in the right order so you can see them all properly.
So that's what z-fighting is, kiddo. It's when the computer gets confused about which object should be in front and which should be behind, and it can make the image on the screen look glitchy.